Issnol l)c<>i-iiihtr 11, V.Hl. 

U. S. DEPARTMENT OF AGRICULTURE. 
8 D FOREST SERVICE— BULLETIN 102. 



HENRY S. GRAVES, Forester. 



^i'^ 



THE IDENTIFICATION OF IMPORTANT 
NORTH AMERICAN OAK WOODS, 

BASED OxN A STUDY 
OF THE ANATOMY OF 
THE SECONDARY WOOD. 



BY 



GEORGE B. SUDWORTH, Dendrologist, 



CLAYTON D. MELL, Assistant Dendrologist, 





WASHINGTON : 

GOVERNMENT PRINTING OFFICE. 

1911. 



r 



Issued December 11, 1911. 



U. S. DEPARTMENT OF AGRICULTURE, 

FOREST SERVICE — BULLETIN 102. 



I^u 



HENRY S. GRAVES, Forester. 



THE IDENTIFICATION OF IMPORTANT 
NORTH AMERICAN OAK WOODS, 



BASED ON A STUDY 
OF THE ANATOMY OF 
THE SECONDARY WOOD. 



ff? 



^\r 



BY 



GEORGE B. SUDWORTH, Dendrologist, 



.>A 



^K " ' 



CLAYTON D. MELL, Assistant Dendrologist. 




WASHINGTON : 

GOVERNMENT PRINTING OFFICE. 

1911. 




.0 



,ETTER OF TRANSMITTAL. 



United States Department of Agriculture, 

Forest Service, 
Washington, D. C, Augusts, 1911. 
Sir: I have the honor to transmit lierewith a manuscript entitled 
"The Identification of Important North American Oak Woods," by 
George B. Sudworth, Dendrologist, and Clayton D. Mell, Assistant 
Dendrologist, and to recommend its publication as Bulletin 102 of 
the Forest Service. 

Kespectfully, Henry S. Graves, 

Forester. 
Hon, James Wilson, 

Secretary of Agriculture. 
2 



CONTENTS, 



Page. 

Need for means of identifying the various oaky 7 

Preparing wood for examination 9 

Gross strneture of oak woods 10 

Principal parts of the oak stem 10 

Sapwood and heartwood 10 

A nnual ri ngs of growth 11 

Pith 13 

Pith rays 13 

Minute structures of oak woods 15 

Vessels or pores 15 

Tracheids 17 

Wood fibers 18 

Wood-parencliyma fibers 18 

Pith-ray cells .• 20 

Structural characters used for identification 21 

Analytical key for identification of oaks 22 

Characteristics of the different oak woods 24 

Laurel oak, Quercus laurifolia 24 

Gambel oak, Quercus gambelii 25 

Pacific post oak, Quercus garryana 26 

Valley oak, Quercus lobata 26 

Netleaf oak, Quercus reticulata 28 

Arizona white oak, Quercus nrizonira 29 

Post oak, Quercus vi'mor 29 

Swamp white oak, Quercus pJatunokks 30 

Emory oak, Quercus emoryi 31 

California black oak, Quercus calif or nica 32 

"White oak, Quercus alba 33 

Bur oak, Quercus macrocarpa 34 

Durand oak, Quercus breviloba 35 

Willow oak, Quercus phellos '. 35 

Overcup oak, Quercus lyraia 37 

Cow oak, Quercus michauxii 37 

Chestnut oak, Quercus prinus 38 

Chinquapin oak, Quercus acuviinata 39 

Shingle oak, Quercus imbricaria 41 

Water oak, Quercus nigra 41 

Turkey oak, Quercus catesbxi 42 

Spanish oak, Quercus digitata 43 

Blackjack oak, Quercus marilandica 44 

Scarlet oak, Quercus coccinea 45 

Bluejack oak, Quercus brevifolia 46 

Pin oak, Quercus palustris 46 

Texan oak, Quercus texana 48 

Yellow oak, Quercus velutina 48 

3 



4 CONTENTS. 

Characlerislics of the dift'erout, oak vvooda — Oonliiiued. Page. 

Red oak, Quercus rubra 49 

California live oak, Quercus agri/olia 51 

Highland live oak, Quercus wislizeni 51 

Canyon live oak, Quercus chrysolepis 53 

Blue oak, Quercus douglasii 53 

Tanbark oak, Quercus densijlora 54 

Live oak, Quercus virgiidana 55 



ILLUSTRATIONS. 



'I'EXT FKJUKK.s. 

Page. 

Fig. 1. Chestnut oak, transverse section of 11 

2. Blue oak, transverse section of 12 

3. Spanish oak, tangential section of . 14 

4. Blackjack oak, radial section of 14 

5. Vessel segment 16 

6. Longitudinal section of portions of two wood lilxMv 16 

7. Tracheid showing bordered pits 16 

8. Wood fil)ers 19 

9. Wood-parenchyma fiber 19 

10. Crystalline masses filling cell cavities 19 

11. Laurel oak, transverse section of 25 

12. Gambel oak, transverse section of 25 

13. Pacific post oak 27 

14. Valley oak 27 

15. Netleaf oak 28 

16. Arizona white oak 28 

17. Post oak 30 

18. Swamp white oak 31 

19. Swamp white oak 31 

20. Emory oak 32 

21 . California black oak 32 

22. White oak 33 

23. Bur oak 34 

24. Bur oak 34 

25. Durand oak 36 

26. Willow oak 36 

27. Overcup oak 38 

28. Cow oak 38 

29. Chestnut oak 39 

30. Chinquapin oak 40 

31. Chinquapin oak 40 

32. Shingle oak 42 

33. Water oak 42 

34 . Turkey oak *. 43 

35. Spanish oak 43 

36. Blackjack oak 45 

37. Scarlet oak 45 

38. Bluejack oak 47 

39. Pin oak 47 

40. Texan oak 49 

41. Yellow oak 49 

42. Red oak 50 

43. California live oak 5u 

44. Highland oak 52 

45. Canyon live oak 52 

46. Rock oak 54 

47. California tanbark oak 54 

48. Live oak 55 

5 



THE IDENTIFICATION OF IMPORTANT 
NORTH AMERICAN OAK WOODS. 



NEED FOR MEANS OF IDENTIFYING THE VARIOUS OAKS. 

This bulletin, the first of a series dealing with the distinguishing 
characters of North American woods (exclusive of Mexico), is pre- 
pared as an aid in the identification of the principal oaks, which 
have received first consideration because they are so widely useful. 
Other groups of woods are to be taken up in order of their commer- 
cial importance. 

While this work is designed for the assistance of all students of 
woods, special effort has been made to render it helpful to manu- 
facturers of lumber, architects, builders, and other wood users. It 
is felt, however, that wood users are likely to derive the greatest 
assistance from the illustrations, by comparing them with the woods 
to be identified, rather than by trying to use the key, which is intended 
mainly for trained students. With the conviction that a very large 
number of wood users can be helped to recognize at least a great 
many woods, the endeavor has been to present for each wood all 
available simple characters, carefully combined with such of the less 
easily observed, finer distinctions as the ordinary student can reason- 
ably be expected to master. 

The wood user's need of a reliable means of recognizing commercial 
woods has become greatly emphasized in recent years because of the 
enormous demand for standard kinds and species of woods. This 
increased use is necessitating, in some cases, the substitution of 
similar or entirely different woods for many of the well-known and 
long-used ones, the supplies of which no longer meet the demand. 
Some of the substitutes offered are as good as the standard timbers, 
while others are inferior to them. However this may be, the fre- 
quent discovery by consumers that they have not received the woods 
ordered has led to a great many difficulties and to serious contro- 
versies involving expensive lawsuits. In many instances manu- 
facturers believe that in substituting, for example, the woods of 
several different species of the white oaks for that of the true white 
oak (Quercus alba) they are doing no injustice to purchasers, and this 
belief is reasonably supported by facts. Much depends upon the 

7 



8 TDENTIFTCATION OF NORTH AMERICAN OAK WOODS. 

use made of the timber. No one could deny that for some purposes 
the woods of cow oak (Quercus micJiauxii), overcup oak (Q. lyrata), 
post oak (Q. minor), bur oak (Q. macrocarpa), swamp wliite oak {Q. 
platanoides) are as good as that of white oak. But the substitution, 
for example, of the somewhat similar black and red oaks for true 
wliite oak is less easily defended, because these substitutes are very 
different in quality from any of the white-oak woods. 

With the numerous oaks, therefore, as with many other woods 
the consumer has occasion to distinguish, such superficial characters 
as color, feel, odor, hardness, weight, etc., can not be depended upon 
alone as distinctive, because they vary not only with the age of the 
tree but also according to the soil in which the tree grew and the season 
and manner of cutting. The butt log differs from the top log, the 
heartwood from the sapwood, and the wood of a rapidly grown tree 
fi'om that of a less rapidly grown one of the same species. 

Wliile the practical woodworker recognizes the woods with which 
constant work has made him familiar, his knowledge of other woods 
is necessarily limited. Confronted with the necessity of distin- 
guishing the few oak woods he knows from a larger number of differ- 
ent species, the characters he has long and safely relied upon are often 
insufficient because they may be common to the wood of some of 
the oaks with which he is unfamiliar. Thus a carefully selected, 
well-seasoned piece of water oak (Q. nigra) may be so similar in color 
and general appearance to some grades of white oak as to deceive not 
a few unacquainted with the structural characteristics of all our oaks. 

Another difficulty that may be encountered by one who depends 
entirely upon an empirical knowledge of woods is to prove his con- 
victions regarding the identity of a wood. For want of exact knowl- 
edge of the anatomical characteristics of the wood in question, he 
can only insist upon liis opinion. It happens in actual practice that 
one inspector passes as white oak a shipment composed of white oak, 
black oak, and red oak, and his judgment is challenged by another 
inspector, yet in such an event neither is able to do more than assert 
his opinion. 

It must not be understood that a study of the structural characters 
of woods always renders identification easy. It is sometimes ex- 
tremely difficult to find characters that distinguish the woods of 
closely related trees, which may be abundantly distinct in their 
flowers, fruit, and foliage. It is comparatively easy to point out 
simple characters wliich distinguish oak from other woods. More- 
over, it is not difficult to find characters that will separate the white 
oaks (annual fruiting species) from the black and red oaks (biennial 
fruiting species). The task, however, of pointing out easily observed 
distinctions that can be relied upon to separate the woods of different 
species of wliite oaks, black oaks, and red oaks is difficult, and, in a few 
instances, impossible without the aid of the high magnifying power 



PREPARING WOOD. 9 

of a compound microscope. This is because some of the minute 
structural characters, easily demonstrated when greatly magnified, 
can not be seen under the low magnifying power of a simple pocket 
lens. However, the need of liigh magnification is confined clfiefly to 
little-known species, with which the practical wood user is not Ukely 
to meet. 

Of the approximately 300 different species of oaks known in the 
world, about 53, exclusive of varieties and hybrids, occur within the 
United States. Three or four of these are mere shrubs, while the 
remainder are small, medium, or large sized trees. The 35 oaks 
described in tliis publication include all of the commercially useful 
ones and a number of other species, the woods of wliich ars likely to 
become more or less useful in the future. The remaining 15 species 
are excluded from the present treatise because their woods are of 
inferior quahty or the trees occur in such limited quantities as to be 
of little or no economic importance. 

The illustrations accompanying this bulletin were made by out- 
lining with a pen photographs of enlarged transverse sections * of 
the wood, and they show the exact appearance of each section as 
seen under a microscope magnifying the structure 20 times its natural 
size. The illustrations are so arranged that the pith rays run up and 
down, and the outside of the annual layer of growth stands toward the 
top of the page. 

Structural characters of the wood having the most distinct value 
for identification are confined principally to transverse sections, in 
which the size, form, arrangement, and other relations of elements 
are clearly shown. The greatest aid will be derived, therefore, by a 
careful comparison of the smoothly cut end of a block with the 
illustrations. Radial and tangential sections were also studied for 
the purpose of discovering any distinctions which these views of the 
wood might ofter. A great many measurements of the fibers of each 
species, to be seen only in these sections, were taken, and their average 
length computed. These are shown in Table 1 on page 56. 

PREPARING WOOD FOR EXAMINATION. 

In preparing a piece of wood for examination with the pocket 
lens it is necessary to cut a smooth surface approxunateh' at right 
angles to the vertical axis of the specimen. If the knife is not sluup 
the surface of the cut will be rough and show but little of the char- 
acteristic structure. With a specimen carefully prepared in this 
way, the observer will be surprised to see how much of detail in the 

1 Preparatory to sectioning, small blocks of wood, of about one-half cubic centimeter, were first boiled in 
water until they were thoroughly saturated and partially softened, after which they were placed in a dilute 
solution of hydrofluoric acid for about 10 days in order to dissolve out the silicates. After thoroughly 
washing the blocks in water, microscopic sections, 8 to 12 micro-millimeters thick, were cut from them with 
a microtome. These sections were then double-stained in safranin an^ Delafields hsemato.xylyi and 
mounted, in the susual way, in balsam, on glass slides. 

7718°— Bull. 102—11 2 



10 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

wood stnicture a small pocket lens reveals. By using the most pow- 
erful form of an aplanatic tiiplet pocket lens a still better view of 
the structure can be had. 

GROSS STRUCTURE OF OAK WOODS. 

PRINCIPAL PARTS OF THE OAK STEM. 

^lany are familiar with the prmcipal parts of an oak stem as shown 
on a freshly cut stump. These parts comprise, first, the bark: sec- 
ond, the sap wood; third, the heartwood; and fourth, the pith. 
Throughout the wood of the stem there are more or less distinct 
and irregularly concentric lings of varying thickness. These are 
annual lings of growth. Running from the i)ith or center of the 
stem to the bark are spoke-like lines, which are pith rays. These 
different tissues afford distinctive features as they appear m close 
union, and are therefore briefly described below, so that the reader 
may become familiar with their characters and arrangement as a 
means of classifying and identifying different species. 

SAPWOOD AND HEARTWOOD. 

A transverse section of the stem of an old oak ti-ee shows two dis- 
tinct zones. The outer portion called sapwood (alburnum) (fig. 1, 
s. w.) is of a light color and consists of a more or less thick zone 
immediately beneath the bark (fig. 1, h.); the inner portion kno\vn as 
heartwood (duramen) is generally darker colored (reddish brown to 
yellowish brown), forming a much harder and more durable mass. 
The width of the heartwood increases year by year, but that of the 
sapwood reniams approxmiately the same, for an inner layer of sap- 
wood becomes transformed annually into an outer layer of heartwood. 
This difference between the sapwood and heartwood is always quite 
evident in hardness and color. The heartwood is lifeless and serves 
the tree only as a mechanical support, while the sapwood alone is 
the living part of the tree and the part in which all vital activities 
take place. The heartwood owes its darker color and its hardness 
and durability to the infiltration of dark-colored chemical sub- 
stances, such as gums and resinous substances, which impregnate 
the cell cavities and frequently fill up the cavities of the wood fibers. 

The sapwood of the dift'erent species of oaks varies considerably 
in width; for example, it is thin in red oak and thick in Spanish 
oak. It varies also in different trees of the same species, depending 
upon the soil, light, and climatic conditions as well as on the general 
health of the trees. Although color and thickness of sapwood are 
sometimes useful characters in distinguishing different woods, fre- 
quently they can not be depended upon. Moreover, a large })ro})or- 



GROSS STRUCTURE. 



11 



tion of the sawed oak timber reaching the markets consists wholly 
of heartwood. For these reasons the structural characters of the 
heartwood, not different, however, from those of the sapwood, have 
been mainly relied uj>on as a basis for classification. 



ANNUAL RINGS OF GROWTH. 



All North American oaks exhibit in transverse sections more or less 
clearly the so-called zones or annual rmgs of growth (fig. 1, a. r.). 




■--—■p.r. 



Fig. 1.— Transverse section of chestnut oak (J^uercus prinus); &.,bark; s. w., sapwood; the darker inner 
portion is heartwood; a. r., annual ring; p. r., pith ray. Natural size. 

In rapidly growing trees these layers are distinctly marked, while in 
those from dry arid regions of the West, wliere the growing season 
is short, or often restricted to periods of rain, the la3'crs are so narrow 
that they appear to be absent or at least obscured by the mere suc- 
cession of inconspicuous rings composed chiefly of pores (fig. 2). 
The width of the rings varies greatly with the age of the tree, also in 
ditt'erent parts of the same tree and m different trees of the same 
species. Trees growing in the open develop larger crowns, and 



12 



IDENTIFICATION OF NOKTH AMERICAN OAK WOODS. 



consequently manufacture a greater amount of plant food, than trees 
in a dense forest. The mcrease m foliage is accompanied by an 
increase in the rate of diameter growth. It follows, therefore, that 
trees in the oi)en w^ith plenty of growing space develop wide annual 
rings, while those in the forest with limited s])ace for crown develo})- 
ment often form very narrow rings. 

The number of growth rings shown in a transverse section of an 
oak, or any other tree grown in a tem])erate climate, in general indi- 
cates the age of the tree, since normally one ring or layer of growth 
is added to the thickness of the trinik and its branches each year. 
There are, however, frequent influences which disturb tliis geneial 




Fig. 2.— Transverse section of (California) blue oak (Quercus douglasii); h., bark; s. u\, sapwoo'l: the 
dark inner portion is heartwood; p. r., pith ray. Natural size. 

regularity, such as drought or the destruction of the leaves by msects 
during the growing season. The result is a tem])orary cessation of 
growth, and in such a case trees may again })ut forth a new set of 
leaves and start growth anew during the same season. This usually 
results in the formation of another ring of pores (the characteristic 
growth at the beginning of the season) similar to the normal early 
wood. This second or newly formed layer is called a "false ring." 

Annual rings of growth consist of an inner and more porous por- 
tion known as early wood (fig. 32, e. w.) and an outer and denser 
portion called late wood (fig. 32, Z. w.). These more or less sharply 



GKOss strttctuhe. 13 

contrasted parts of tlie annual rings are a result of tlie development 
of a gradually dimishing number of large vessels duiing the latter 
])art of the season's growth. The denser portion, therefore, encases 
the more porous part, or early wood, which contains elements with 
larger diametei-s and thinner walls. These elements are called 
vessels, which serve as conducting tissue. The de.nse late wood, 
which ordinarily forms the greater part of the annual ring, is com- 
posed largely of closely packed, thick-walled wood fibere wliich give 
the wood strength, weight, toughness, and elasticity. The wood of 
slowly grown oaks, and particularly that of old trees, is often exceed- 
ingly ''brash," because it contains a very large proportion of early 
(porous) W'Ood. 

The proportion of late to early wood is usually greater in fast- 
growing than in slow-growing trees. This is true especially of the 
wood formed near the base of the stem, where it is denser and heavier 
than that in any other portion of the tree. There is less early wood 
formed at the base of the stem than farther up, because growth com- 
mences nearly a month later at the base. The strongest, densest, 
and toughest oak timber is that grown in the open, where the full 
enjoyment of side light })roduces wide rings. 

PITH. 

A transveree section of the stem of an oak exhibits a Ught-brown 
speck in the center commonly known as the pith, wliich is quite 
small and does not increase in size as the tree growls older. (See 
center of figs. 1 and 2.) The cells composing the pith are thin 
walled, usually of uniform diameter, and gradually become emptied 
of their contents. In some oaks these elements, technically known 
as parenchyma cells, continue to live for a number of yeare, later 
becoming lignified and tliickened with age, so that it is often difficult 
to detect the pith in steins of old trees. In transvei-se section the 
pith of most oaks is pentagonal in outline. This character is useful 
in distinguishing oaks as a group from other woods. 

PITH RAYS. 

Pith rays constitute the spoke-like lines to be seen more or less 
conspicuously on the transverse section of the oak stem (figs. 1 and 
2, J), r.). They form the so-called "silver gram" w^ell knowTi among 
caipenters. The large (primaiy) pith rays are merely spokes, as it 
were, joining the pith and bark. Each spoke is from a few to 25 or 
more ray cells in width, and from 100 to 600 or more cells in height 
(lig. 3, p. p.r.). Each succeeding year other rays are formed, which 
extend from the point where they originate to the peiipheiy of 
the stem. These are called small (secondaiy) pith rays because 



14 



rOENTIFICATION OF NORTH AMERICAN OAK WOODS. 



tlicy started later in tlio life of the tree, but tliey serve the same 
l)iii1)oses and bear the same rehitionship to other tissue of the stem 
as the hirge pith rays, except that they do not extend inward to the 
pith (fig. 3, s. p. r.). The small rays are seldom more than one cell 
wide, but are from a few to 20 or more cells high. On a radially 
split surface of oak wood the large pith rays may be seen with the 
unaided eye as horizontal bands traversing the wood from within 
outward; the small rays can not be seen with the unaided eye. 

The presence of two kinds of ra3^s in the woods of all North Ameri- 
can oaks furnishes another helpful generic distinction. Investiga- 






FiG. 4. 
Fig. 3.— Spanish oak (Quercus dlgilata). Tangential section showing large (/>. p. r.) ami small pith rays 

(.S-. p. r.) magnified about 20 diameters. 
Fi(i. 4.— Blackjaeli (QwercM* marilandka). Radial section showing pith rays (p. r.) magnified 20 diameters. 

tions show, however, that the charactei's of the pith rays in oaks are 
not sufficiently constant to distinguish tlie different species. The 
number of pith rays is largely dependent upon the age of the tree, 
and they are most abundant m wood of the first layer of growth. 
Proceedmg from this toward the bark they gradually dimmish in 
number per unit area for a certain period of yeai*s, and then agam, 
later in the hfe of a tree, they commence to increase in number. 
Moreover, different individuals of the same species show a marked 
variation in the number of pith rays. With reference to the number 
of rays for the dilTerent species of oaks, the figures obtained by actual 
counts are exceedingly variable. Again, the height of the pith rays 
ill the same individual and in different individuals of the same 



MINUTE STRUCTURES. 15 

Species IS so variable that it can not be accepted as a trustwortliy 
mark of distinction. As the trees grow older the pith ra^'s gradually 
mcrease in height. Evergreen oaks, and particularly veiy slow- 
growing species or those growing on dry arid soil, develop rather lo^y 
and wide rays, which have blunt ends above and below. This 
applies particularly to oaks of the Rocky Mountain and Pacific 
slope regions. The deciduous oaks, growing in rnoist, alluvial soils, 
develop high and narrow pith rays which have niore or less acute 
ends above and below. This applies particularly to the eastern 
oaks (compare figs. 1 and 2). For a difference in comparative width 
of pith rays in the two arbitrary groups referred to above see figures 
1 and 2. 

MINUTE STRUCTURES OF OAK WOODS. 

Tlie minute elements which make up the wood of oaks will be 
described separately, in order to present a clear general view of the 
part they play in the composition of the wood. Size, shape, relative 
proportion, and grouping of the elements are more or less charac- 
teristic in all woods, and a clear idea of these elements can be ob- 
tained only by a study of the transverse, radial, and tangential sec- 
tions under a compound microscope. Five different kinds of ele- 
ments can then be distinguished; namely, vessels, tracheids, wood 
fibers, wood-parenchyma fibers, and pith-ray cells. 

VESSELS OR PORES. 

The vessels differing in size and arrangement may be seen with the 
unaided eye in a transverse section of the wood of both deciduous and 
evergreen oaks. These vessels, commonly known as pores, and tech- 
nically as tracheae, make up chiefly the inner and more porous part of 
the annual ring of growth. They vary from less than 0.1 to more 
than 0.6 of a millimeter ^ in diameter and are composed of tube-like 
segments arranged longitudinally end to end; the cavities of the 
vessels communicate directly with one another, while the adjoining 
obliquely formed ends are perforated by horizontal pits (fig. 5a, a.), 
or are completely absorbed (fig. 5, a.) so that the rows of cells or vessel 
segments finally form long, continuous tubes. These oblique cross 
walls (fig. 5, c. w.) between the vessel segments not infrequently have 
scalariform (ladder-like) perforations (fig. 5a, a.). Individually the 
segments arc often short and barrel-shaped, though they usually have 
rather obliquely formed end walls which always face toward the pith 
rays. The segments in late wood are about twice as long as they are 
wide, but in the early wood their diameter sometimes exceeds their 
length. In a longitudinal section of oak wood they appear as minute 

1 One millimeter is equal to about one twenty-fifth of an inch. The metric system is used in this work 
in order to avoid large fractions. 



16 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



channels. The vessels which are arranged in radial rows (transverse 
section) in the late wood have a successively smaller diameter than 
those formed earlier, and with this gradual diminution in diameter 



bp.. 




RsS- 




fi£ 6, 



^'"''fed 






f^e fo 



F.i.k 




ns7 



Fig. 5. — Vessel segment showing oblique cross walls (c. w.) completely absorbed at a; b. p., bordered pit. 

Magnified about 100 diameters. 
Fig. 5a.^VesseI segment showing oblique cross walls (c. w., partly absorbed); a, scalariform (ladder-like) 

perforations; 6. p., bordered pits. Magnified 100 diameters. 
Fig. (5. — Longitudinal section of portions of two wood fibers showing simple pits (s. p.); c. w., cell wall; 

r. c, cell cavity. Magnified about 100 diameters. (See also fig. 8.) 
Fig. 6a. — 1. Longitudinal section of a bordered pit (&. p.); t, torus. 2. Surface view of pit; corresponding 

regions are connected by dotted lines. Magnified about 500 diameters. 
Fig. 7.— Tracheid showing bordered pits (6. p.). Magnified about 75 diameters. 

there is generally a corresponding increase in the thickness of the walls 
of these elements, a factor which adds mechanical support to the tree. 
The size and arrangement of these small vessels in the late wood also 
afford, to some extent, distinctive features. 



MINUTE STEUCTUEES. 17 

The side walls of vessels become sculptured or pitted at maturity, 
and the commonest form of sculpture is the result of small areas in the 
walls called pits remaining unchanged during the thickening process 
called lignification. These unthickened portions may be seen with 
the aid of a microscope in a longitudinal section of oak wood. The 
pits are of two kinds, simple and bordered. A simple pit is a very 
small thin portion of the cell wall, forming a short, regular, and radi- 
ally directed canal within the cell wall (fig. 6, s. j)-)- A bordered pit 
is formed in a similar manner, but the walls of the canals always 
make a distinct angle, thus leaving the short canal wide on the outside 
and narrow toward the center of the cell (fig. 6a, h. p.). Pits are shal- 
low, depending upon the thickness of the cell walls, while in outline 
they are elliptical, elongated, or rarely rectangular. In a few cases 
they are so extended as to form thickened ridges between the pits 
and appear like the rungs of a ladder; hence the name scalariform 
markings. This mode of thickening is sometimes seen in the sap- 
wood of evergreen oaks. 

After vessels lose their sap and the air in them is rarefied, tyloses 
(very delicate partition-like walls) begin to form and to block up the 
cavities, rendering the heartwood impervious, or nearly so, especially 
in most species of the white oak group, to the entrance of fluids. 
Tyloses consist of parenchymatous (pith-like) tissue (fig. 4, t.) which 
has been forced out of the swelling (turgescent) adjacent thin-walled 
pith-ray cells or wood-parenchyma fibers into the lumina or channels 
of the vessels. The thin membranes (original, unthickened portions 
of cell wall) within the bordered pits, which separate the contents of 
the adjacent parenchyma cells, are ruptured by the swelling of the 
pith-ray cells. This parenchymatous tissue commences to grow 
very rapidly and in a short time fills up the cavities of the vessels. 
Tyloses are particularly abundant in v^ood of oaks belonging to the 
white oak group, and not infrequently serves to separate the white 
from the black oaks. 

TRACHEIDS. 

Tracheids (fig. 7) are usually found immediately adjoining the ves- 
sels. They are slight modifications of the wood fibers (described 
below), and differ from them in having thin walls with numerous 
more or less narrow and oblique or horizontal bordered pits. These 
pits occur irrespective of whether the contiguous elements are ves- 
sels, tracheids, or wood fibers. Tracheids are single fiber-like ele- 
ments, and are, therefore, easily distinguished, whereas vessels are 
formed by a fusion of cells placed end to end. In transverse sections 
it is more difficult to separate them from the very small vessels. 
The ends of these tracheids are often curved, especially if the tracheid 
terminates immediately above or below a pith ray. They also have the 
7718°— Bull. 102—11 3 



18 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

form of barbed books as seen occasionally in the wood of Quercus 
wislizeni and Q. virginiana. Tracheids are not referred to in the 
description of different species of oak wood, for the reason that they 
are not distinctive features. 

WOOD FIBERS. 

Wood fibers (fig. 8a) are veiy fine, thread-like cells, which com- 
pose chiefly the dark, dense outer portion of the annual ring of growth. 
They resemble the tracheids, though they are longer and sometimes 
have walls so thick that scarcely any cell cavities (fig. 8a, c. c.) remain. 
Wood fibers may be divided into two classes: First, those that are 
unsegmented and either have no pits at all or only a few partially 
developed simple pits; and second, those that are segmented and 
have simple pits in their walls. The segmented wood fibers are found 
very rarely in the wood of oaks, being restricted mainly to the wood of 
Quercus garryana, here present in an intermediate form of element 
between wood fibers and wood-parenchyma fibers discussed later. 
The narrow, thick-walled, and unsegmented wood fibers make up the 
greater portion of the mass of the wood of oaks (fig. 8). In Quercus 
lyrata wood fibers with wide cavities and rather thin walls form the 
greater part of the late wood, which accounts for its light weight and 
softness. Thick- walled, compactly arranged elements render the 
wood heavy, as in the case of most evergreen oaks. This is particu- 
larly true of the live oaks, Quercus chrysolepis and Q. virginiana. 
The cavities of the wood fibers are widest in Q. cateshsei, Q. lyrata, 
Q. nigra, and Q. phellos. On this account the wood of these oaks is 
softer and is worked more easily than that of the other species. The 
narrowest or thinnest wood fibers are found in Q. minor and Q. 
platanoides. The average length of wood fibers of all the North 
American oaks is approximately 1.3 ^ millimeters (about ^V of an 
inch). The longest fibers are found in the wood of Q. coccinea, while 
the shortest occur in Q. arizonica and Q. rubra. 

The ends of some wood fibers are flattened and sometimes even 
forked and with a saw edge (fig. 8b, a and h). Fibers usually run 
parallel to one another, but there may be seen in some of the western 
species a decided interweaving with one another, which produces 
"cross-grained" wood, difficult to split. 

WOOD-PARENCHYMA FIBERS. 

The individual cells of wood-parenchyma fibers resemble the pith- 
ray cells, ])ut they are grouped in vertical rows instead of horizontal 
rows (figs. 9 and 10). They predominate in the more porous parts 

1 All dimensions of wood elements given in this work are averages not only of a great many different 
measurements of elements from a large number of samples, but also of elements from different parts of the 
same specimens. It is advisable, therafore, in attempting to trace down a piece of oak wood carefully to 
examine slides made from ditTerent parts of a specimen. 



MTNUTE STRUCTURES. 



19 



of the annual rings of growth and often closely surround the vessels 
and tracheids. In the dense late wood, wood-parenchyma fibers 
form conspicuous, tangentially arranged bands between irregular, 



,S p. 




Fes S 




- -sp 



'^' ^ fS- 



Fig. 8.— Transverse section of wood fibers; p. r. c, pith ray cell; c, crystal of calcium oxalate; w.f., wood 

fibers; s. p., simple pit. Magnified about 17.5 diameters. 
Fig. 8a.— Wood fiber showing thick walls (c. «'.), and a small cavity (e. c); s.p., simple pit. Magnified 

about 150 diameters. 
Fig. 8b.— a, Wood fiber forked at one end; 6, wood fiber with a saw-toothed edge at one end; «. /)., ol)lique 

simple pits. Magnified about 103 diameters. 
Fig. 9.— Wood-parenchyma fiber showing individual cells (c); s. p., simple pits. Magnified about 125 

diameters. 
Fig. 10.— Crystalline masses (idioblasts) completely filling the individual cell cavities; c, crystals of calcium 

oxalate; s. p., simple pits. Magnified about 125 diameters. 

compact, radial rcnvs of thick-walled wood libers. On a ])erfectly 
smooth transverse section of oak wood, having well-defined late wood, 
these bands of wood-parenchyma fibers can be detected with the 



20 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

unaided eye (fig. 15, w. 'p. J.). When greatly internn)ted by wood 
fibers, the wood-parenchyma bands become indistinct and can be 
distinguished only by means of a microscope. 

In late wood these elements are usually round in transverse section, 
but in early wood, where unequal pressure is exerted upon them by 
the rapid growth of vessels, they are flattened and their usual shape 
and arrangement are often greatly disturbed. The size, shape, and 
niarkmgs of wood-parenchyma fibers in late wood of difi'erent oaks 
vary but little. The pits are chiefly simple (fig. 9, s. ]).), though 
occasionally wood-parenchyma cells are found that have bordered 
pits, as in the case of some evergreen oaks. The abundance, arrange- 
ment, and the particular relation these elements bear to one another 
are, however, important in distinguishing the wood of the dift'erent 
species of oalvs. 

Wood-parenchyma cells usually contain starch, and also a certain 
quantity of tannin, but these facts are of little value in identifying 
the different oaks, since the amount and nature of cell contents depend 
greatly upon the age of the tree, the time of the year the tree was cut, 
and the part of the tree from which the wood was taken. 

Crystals of calcium oxalate (fig. 10, c.) are found in all paren- 
chymatous tissue of all species of oaks. They are developed smgly 
in the cells and belong to the tetragonal crystal system. These 
ciystals are only slightly soluble even in the strongest acids and are 
very clearly visible under the high power of the microscope both in 
transverse and longitudinal sections. In pith-ray cells they are often 
found in rows of from 3 to 6, while in wood-parenchyma fibers they 
occur in much longer rows, particularly in the early wood, and are 
technically known as idioblasts (fig. 10). In such cases the whole 
cell becomes merely a repositoiy for the crystal. Such crystals are 
especially frecpient in the wood of Quercus arizonica, Q. calijornica, 
Q. douglasii, Q. emoryi, Q. gamhelii, Q. garryana, Q. lohata, Q. lyrata, 
Q. reticulata, Q. texana, and Q. virginiana. Individual sam}>les of 
other oaks are often found, however, that contain as many ciystals 
as those just named. A careful investigation has sho^\^l that the 
woods of evergreen oaks, and especially those of the Roclcy Mountain 
and Pacific coast regions, contain more ciystals than those of the 
eastern deciduous oaks in general. 

PITH-RAY CELLS. 

Pith-ray cells have already been briefly described in c(Hmection 
with pith rays. They occur in from one to many rows closely packed 
together, and individually are arranged end to end with their long 
axes in a radial direction. In a transverse section these radial rows 
of parenchyma cells can be seen as narrow but more or less distinct 



STRUCTURAL CHARACTERS. 21 

lines; the larger ones (fig. 3, p. p. r.) extending from the pith to the 
peripheiy of the stem. The width and height (tangential section) 
of these rays are entirely dependent upon the age of the tree and 
upon the distance from the pith or peripheiy of tlie stem. In a 
tangential section the small pith rays are seen in vertical rows of a 
single cell in width, and from a few to 20 or more cells in height (fig. 
3, s. p. r.). Where these cells are m contact with one another or with 
wood-parenchyma fibers the pits are simple (fig. 8, s. p. in p. r.), but 
if they lie next to vessels or tracheids the portion of the converging 
pits in vessel walls is bordered, and that of the ray cells is simple. 

STRUCTURAL CHARACTERS USED FOR IDENTIFICATION. 

The technical generic name of oak, Quercus, is derived from the 
Celtic words quer, meaning "fine," and cuez, "tree," in reference to 
its highly esteemed qualities. The genus Quercus belongs to the family 
Fagacese, wdiich contains three other genera, Fagus, Casfanea, and 
Castanopsis, native to the United States. The oaks are trees and 
shrubs distributed widely over the northern hemisphere and in parts 
of Java and South America. The different species vary greatly 
in the form and character of their leaves, fruit, bark, and general 
appearance, but there are no such marked constant characters as 
these present in the woods of oaks by means of which they can be 
readily distinguished. There is much variation in the appearance of 
the wood of the different oaks, but the woods of different trees of any 
particular species may also vary so remarkably in appearance, 
depending upon the conditions under which the trees grew, that it 
often requires very careful study to identify them. 

The woods of the oaks described in this work are classified according 
to differences in the form and arrangement of the large and small 
vessels (pores), wood fibers, and wood-parenchyma fibers, also 
according to the width and outline of the annual rings of growth, 
and by a comparison of the early and late wood composing each ring. 
Microscopic characters have been resorted to only when the gross 
characters are insufficient for identification. A number of the ever- 
green oaks, native to high, dry plains of the Southwest, have hard 
wood, and show exceedingly narrow layers of growth and very wide 
pith rays. A few of our oaks have a very wide natural range of 
growth, which accounts in a great measure for the variability in the 
character of their woods. Bur oak, for instance, ranges from Nova 
Scotia westward to Manitoba and southwestward to Texas. Witliin 
this range it occurs both in the form of chaparral and as a large tree, 
and the character of the wood varies greatly with the different situa- 
tions to which it has become adapted (figs. 23 and 24, p. 34). 



22 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

ANALYTICAL KEY FOR THE IDENTIFICATION OF IMPORTANT 
NORTH AMERICAN OAKS, BASED ON CHARACTERS OF THE 
SECONDARY WOOD.' 

A. Marked distinction between early and late wood. 

1. Pores abruptly diminishing in size from early to late wood; large pores contain 
considerable tyloses. 

WHITE AND WILLOW 0.\KS. 

Pores in early wood arranged mo.^tly in 1 tangential row or rarely in 2 distinct 
rows; pore.-i in lale wood half the size of those in early wood, few and scat- 
tered 1. Quercus laurifolia (p. 24). 

Pores in early wood arranged in 1 to 3 tangential rows; pores in late wood less 
than half the size of those in early wood. 
Pores in late wood 0.05 ^ millimeter or less in diameter and arranged irregu- 
larly or in single or double radial rows. 
Pores in late wood mostly forming single radial rows; tangential l)ands of 

wood-parenchyma fibers conspicuous 2. Quercus gamheUi (p. 25). 

Pores in late wood mostly forming double radial rows; tangential bands of 
wood-parenchyma fibers less conspicuous, except in 5. 
Radial rows of small pores surrounded by v>'ood-parenchyma fibers; these 
rov.-s becoming wider near the periphery of the annual ring. 

.3. Quercus gnrryana (p. 2G). 
Walls of ]V)res in early wood thicker than those in the late woo;l. 

Crystals of calcium oxalate rare 4. Quercus lobata (p. 26). 

Walls of pores in earh- wood thinner than those in the late wood. 
Crystals of calcium oxalate very numerous. 
Pores in early wood vary from 0.05 to 0.2 millimeter in diameter; 
tangential bands of wodd-jiarenchyma fibers very wide. 

5. Quercus reticulata (p. 28). 
Pores in early wood vary from 0.2 to 0.3 millimeter in diameter; 

tangential bands of wood-parenchyma fibers very inconspicuous. 

6. Quercus arizonica (p. 29). 
Pores in late wood more than 1 millimeter in diameter and arranged chiefly in 

single radial rows. 
Radial rows of pores extending to periphery of annual rings of growth. 
Pores in early wood round and from 0.15 to 0.25 millimeter in diameter. 

7. Quercus minor (p. 29). 
Pores in early wood chiefly ellii)tical and 0.2 to 0.3 millimeter in diameter. 

S. Quercus platanoides (p. 30). 
Radial rows of pores rarely extending to ])eri])hery of annual rings of growth. 

9. Quercus emori/i (p. 31). 
Pores in late wood very variable and arranged chiefly in double, radial rows. 
Pores uniformly large and rows invariably extending to the periphery of 

annual rings of growth 10. Quercus caUfornica (p. 32). 

Pores very irregular in size and radial rows rarely extending to the periphery 
of annual rings of growth. 



! Sapwood and heartwood, the strictly woodj^ parts of a tree stem, are collec-tively known as secondary 
wood, a technical name given to mature wood because its formation follows in the order of tlevelopment 
the growth of tissue known as primary wood, which is intermediate in character between the purely paren- 
chymatous tissue of ])ith and fully matured wood. The general order of growth in a tree stem is therefore, 
first, the production of the purely parenchymatous tissue of pith; second, the formation of primary wood; 
and third, the laying on of secondary wood. Following the production of pith and primary wood comes the 
formation of the so-called "cambium ring," a generative layer of thin-walled cells, which develops second- 
ary wood on its inner side and bark on its outer side. 

2 See footnote 1, p. 15. 



ANALYTICAL KEY, 23 

Wood-parenchyma fibers in late wood arranged chiefly in conspicuous, 
double, tangential bands. Tyloses very abundant. 

Large pith rays about 4 millimeters apart 11. (juercus alba (p. 33). 

Large pith rays about 6 millimeters apart. 

12. Quercus macrocarpa (p. 34). 
Wood-parenchyma fibers in late wood scattered rather irregularly, occa- 
sionally in short, parallel, inconspicuous, tangential bands. 
Pores in early wood arranged chiefly in one row, with broad, conspicuous 
radial rows of smaller pores. 

Pores in early wood round or oval 13. Quercus breviloba (p. 35). 

Pores ia early wood strongly elliptical 14. Quercus phellos (p. 35). 

Pores in early wood arranged chiefly in 2 to 3 rows and pores in late wood 

larger than in 13 and 14. 

Radial rows of pores in late wood unusually wide; heart wood dark 

brown with lighter-colored sapwood — .15. Quercus lyrata (p. 37). 

Radial rows of pores in late wood usually narrow^er; heartwood light 

brown, with darker-colored sapwood.. 16. Quercus michauxii (p. 37). 

Pores in early wood arranged in 3 to 5 rows. 

Walls of pores in late wood thin; radial rows of small pores become wider 
toward periphery of annual rings of growth. . .17. Quercus prinus (p. 38). 
Walls of pores in late wood thick; radial rows of small pores become narrower 
toward the periphery of the annual rings of growth. 
Pores in late wood chiefly in single radial rows. 

18. (Quercus acuminata (p. 39); 
Pores in late wood chiefly in double radial rows. 

19. Quercus imbricaria (p. 41). 
2. Pores gradually diminishing in size from early to late wood ; large pores contain 

very little tyloses. 

BLACK OAKS AND RED OAKS. 

Pores in early wood arranged chiefly in 1 to 3 rows. 
Radial rows of small pores usually numerous, double, and somewhat irregular; 
tangential bands of wood-parenchyma fibers very numerous. 

20. Quercus nigra (p. 41). 

Radial rows of small pores usually single and parallel ; tangential bands of 

wood-parenchyma fibers few and inconspicuous. 

Pores in early wood round; wood light brown and strongly tinged with 

orange ; a tree seldom more than 4 decimeters in diameter near the base. 

21. Quercus catesbxi (p. 42). 
Pores in early wood elliptical or oval; wood light brown and faintly tinged 

with red; a tree often G to 8 decimeters in diameter near the base. 

22. Quercus digitata (p. 43). 
Pores in early wood arranged chiefly in 3 to 5 rows.' 

Wood-parenchyma fibers in late wood arranged in conspicuous, tangential 
bands more than one cell wide. 
Pores in early wood very numerous and from 0.2 to 0.4 millimeter in diameter. 

Pores filled with tylo.ses 23. Quercus marilandica (p. 44). 

Pores with very little tyloses 24. (Quercus coccinea (p. 45). 

Pores in early wood less numerous and from 0.15 to 0.25 millimeter in 
diameter. 
Pores in late wood 0.05 millimeter in diameter. 

25. Quercus brevifolia (p. 46). 
Pores in late wood 0.025 millimeter in diameter. 

26. Quercus palustris (p. 46). 



24 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

Wood-parenchyma fibers in late wood scattered irregularly among the wood 
fibers, or sometimes arranged in much interrupted, inconspicuous, tan- 
gential bands one cell wide. 

Wood-parenchyma fibers very abundant in early wood; crystals of calcium 
oxalate numerous in pith ray cells 27. Quercus tcxana (p. 48). 

Wood-parenchyma fibers arranged in two or more double, concentric bands 
around the pores in early wood; crystals of calcium oxalate in pith ray 
cells very rare 28. Quercus velutina (p. 48j. 

Wood-parenchyma fibers grouped irregularly around pores in early wood; 

crystals of calcium oxalate very rare 29. Quercus rubra (p. 49). 

B. Little distinction between early and late wood. 

EVERGREEN OAKS, EXCEPT NO. 33. 

1. Pores chiefly arranged in distinct radial rows. 
Radial rows of pores in late wood usually single. 

Tangential bands of wood-parenchyma fibers distinct. 

30. Quercus arjrifoHa (p. 51). 
Tangential bands of wood-parenchyma fibers rather indistinct. 

31. Quercus wislizeni (p. 51). 
Radial rows of pores in late wood usually double. 

Tangential bands of wood-parenchyma fibers very short and confined to the 
outer portion of the late wood; in early wood these elements scattered. 

32. Quercus chrysolepis (p. 53). 

2. Pores rather uniformly distril)uted throughout the annual layers of growth. 
Pores in early wood twice the size of those in late wood ; annual rings of growth 

very narrow; heartwood dark or nearly black. . .33. Quercus douglasii (p. 53). 
Pores in early and late wood nearly imiform in size; annual rings of growth 

wider; wood very light brown 34. Quercus densiflora (p. 54). 

Pores few, only slightly diminishing, but uniformly distributed across the annual 

rings of growth 35. Quercus virghiiana (p. 55). 

CHARACTERISTICS OF THE DIFFERENT OAK WOODS. 

1. Laurel Oak (Quercus laurifolia Michaux) . (Fig. 11.) 

Heartwood dark brown tinged with red; sap wood thick and some- 
what ligliter colored. Wood hard, heavy, strong, rather coarse- 
grained, and not very dm'able in contact with the soil. Rate of 
growth rather slow, requiring on an average from 10 to 12 years for 
the tree to increase 1 inch in diameter. 

Vessels (lig. 11, v.) in early wood (e. u\) 1 or rarely 2 rows deep, 
round and approximately 0.25 ^ millimeter in diameter, diminishing 
abruptly in late wood (/. w.) to about 0.12 millimeter. Small vessels 
in radial row^s extending to the periphery of the annual ring of 
growth. Wood Jibers (w. f.) very numerous both in the early and 
late wood, averaging 1.34 millimeters long and approximately 0.021 
millimeter wide. Cell walls thick and the cavities rather small. 
Wood-parenchyma Jibers uniformly distributed throughout the entire 
annual ring of growth. In the late wood they are arranged in single, 
irregular, indistinct tangential l)ands. Pith rays: Large pith rays 

1 See footnote 1, p. 15. 



CHARACTERISTICS. 



25 



(Z. p. r.) from 25 to 40 cells wide and from three to four times as 
high and from 2 to 3 millimeters apart; small pith rays {s. p. r.) 
rarely more than 1 cell wide and from a few to 15 cells liigh. 

The wood of laurel oak resembles that of live oak {Q. virginiana), 
but is easily distinguished by its less prominent pith rays and more 
distinct annual rings of growth. 

2. Gambel Oak (Quercus gambelii Nuttall). (Fig. 12.) 

Heart wood dark brown tinged with red; sap wood rather tliin and 
m.uch lighter colored. Wood hard, heavy, strong, close-grained. 







Fig. 11. Fig. 12. 

Fig. 11.— Laurel oakiQuercus laurifoHa). Transverse section through two entire annual rings of growtli; 

a. T., annual nng; e. w., early wood; /. ic, late wood; Z. p. r., largo pith ray; 5. p. r., small pith ray; v., 

vessel; iv.f., wood fiber; w.p./., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 12. — Gambel oak {Quercus gambelii). Transverse section through six entire annual rings of growth: 

e.w., early wood; l.w., late wood; Lp. r., large pith ray; s. p. r., small pith ray; v., vessel; w./.,wood fiber; 

w. p.f., wood-parenchyma fiber. Magnified 20 diameters. 

and fairly durable in contact with the soil. Rate of growth exceed- 
ingly slow, requiring on an average from 15 to 20 years to grow 1 
inch in diameter. 

Vessels (fig. 12, v.) seldom more than 2 rows deep, round or occa- 
sionally in wide annual rings of growth elliptical or oval, and approxi- 
mately from 0.1 to 0.25 millimeter in diameter. Vessel walls in 
early wood thicker than those in late wood. Small vessels in late 
wood abruptly smaller, seldom over 0.025 millimeter, forming from 1 to 
3 single, or rarely double, irregular, radial rows extending across the 
entire width of the annual ring of growth. Woodjihers (w. f.) nu- 
merous in early wood, averaging 1.16 millimeters long and 0.018 milli- 
7718°— Bull. 102—11 4 



26 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

meter wide. Walls exceedingly thick and cavities small. Wood- 
'parenchy ma fibers (w. p. f.) cliiefly surround large and small vessels. 
In outer portion of late wood these cells are arranged in tangential 
bands from 2 to 4 cells wide and near the early wood only 1 cell wide. 
Crystals of calcium oxalate very numerous. Pith rays: Large pith 
rays (I. p. r.) very conspicuous, from 35 to 45 cells wide and from 
three to five times as liigh and from 1.5 to 2.5 millimeters apart. 
Individual cells generalh^ filled ^vdth dark-brown coloring matter 
consisting of starch, tannin, and crystals of calcium oxalate. The 
small pith rays (s. p. r.) only 1 cell wide and from 4 to 15 cells liigh. 
The wood of gambel oak can be distinguished from that of the 
garry oak {Q. garryana), with wliich it may be confused, by its dark- 
brown color. 

3. Pacific Post Oak {Quercus garryana DouglsiB) . (Fig. 13.) 
Heartwood light yellow and clearly distinguished from the tliin 

and nearly white sapwood. Wood is hard, exceedingly tough, close- 
grained, and very durable. Rate of growth rather slow, requiring 
from 12 to 15 years to increase 1 inch in diameter. 

Vessels (fig. 13, v.) in early wood 2 or rarely 3 rows deep, oval, 
with an average radial diameter of 0.35 millimeter and tangential 
diameter of 0.25 millimeter. In late wood (I. w.) they abruptly 
diminish to a uniform size of about 0.05 millimeter in diameter, 
arranged in two wide radial rows surrounded by numerous concen- 
tric bands of wood-parenchyma fibers visible under the compound 
microscope. Walls of small vessels in late wood tliinner than those 
in earl}' wood. Wood fibers {w. f.) on an average 1.3 millimeters 
long and about 0.018 millimeter wide. Walls thick and cavities 
small, occurring in more or less isolated and compact groups between 
the radial rows of small vessels and tangential bands of wood-paren- 
chyma fibers. Wood- pare ncliy ma jihers {w. p. f.) very abundant in 
early wood; also forming concentric bands around the small vessels 
in the radial rows and from 3 to 5 narrow, conspicuous tangential 
bands in late wood. Pith i^ays: Large pith rays (Z. p. r.) are about 
300 cells wide and from four to five times as high and from 3 to 4 
millimeters apart. Small pith rays {s. p. r.) are onl}" a single eel 
wide and. from a few to 20 cells high. 

(See reference under Valley oak to possible confusion of this wood 
with others.) 

4. Valley Oak (Quercus lobata Nees von Esenbeck). (Fig. 14.) 
Heartwood light brown tinged with jxhI; sapwood rather thin and 

much lighter colored. Wood hard, heavy, rather fine-grained, brittle, 
and durable in contact with the soil. Although individual trees of 
this species grow moderately fast, most samples show that from 12 
to 18 years are required for, a tree to grow 1 inch in diameter. 



CHARACTERISTICS. 



27 



Vessels (fig. 14, v.) in early wood {e. w.) 1 to 2 rows deep, round, 
varying from 0.2 to 0.5 millimeter in diameter, and generally filled 
with tyloses (t.); in late wood (I. w.) they become abruptly smaller, 
averaging approximately 0.06 millimeter and are distributed uni- 
formly across the late wood. Wood f hers (w. f.) average about 1.24 
millimeters in length and are chiefly confined to late wood; early 
wood being almost wholly composed of large vessels and wood- 
parenchyma fibers. Cell walls thick with rather small cavities. 
Wood-parenchyma fihers (w. p. f.) abundant in early wood, surround- 




FiG. 13. 



Fig. 14. 



Fig. 13. — Pacific post oak ( Quercus garryana). Transverse section tlirougli one entire annual ring of growth ; 

e. w., early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v., vessel; w.f., wood fiber; 

w. p.f., wood-parenchyma filler. Magnified 20 diameters. 
Fig. 14. — Valley oak {Quercus lobata). Transverse section through three entire annual rings of growth; 

e.w., early wood; Z.w.,late wood; I. p. r., large pith ray; s. p. r., small pith ray; t'., vessel; v.f., wood 

fiber; w. p.f., wood-parenchyma fiber; t., tyloses. Magnified 20 diameters. 

ing large pores; more sparingly found in late wood with an almost 
entire absence of tangential arrangement. Numerous calcium 
oxalate ciystals present. Pith rays: Large pith rays (Z. p. r.) are 
from 10 to 25 cells wide, and from two to six times as high and from 
1 to 4 millimeters apart. Small pith rays (s. p. r.) inconspicuous 
and very irregular on account of the numerous pores which they 
avoid. 

The v/ood of valley oak is distinguished from blue oak (Q. dougJasii) 
by its lighter brown color, and from the similar garry oak (Q. gar- 
ryajia) by the latter's very much wider pith raj's. 



28 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



5. Netleaf Oak (Quercus reticulata Humboldt, Bonpland and Kimth). 
(Fig. 15.) 

Heartwood dark brown and occasionally tinged with red; sapwood 
thick and much lighter colored. Wood hard, heavy, very close- 
grained and not very durable in contact with the soil. Very little 
contrast between early and late wood. Rate of growth very slow, 
requiring from 12 to 18 years to grow 1 inch in diameter. 

Vessels (fig. 15, v.) in early wood (e. w.) from 1 to 3 interrupted 
rows deep, varying in diameter from 0.05 to 0.2 millimeter; those 








L^^Hl >, 





Fig. 15. 



Fig. 16. 



Fig. 15. — Netleaf oak {Quercus reticulata).— Transverse section through two entu-e annual rings of growth; 

e.w., early wood; Z. w.Jatew^ood; Z. p. r., large pith ray; s. p. r., small pith ray; v., vessel; M'./., wood fiber; 

w. p.f., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 16. — Arizona white oali (Quercus arizonica). Transverse section through one annual ring of growth 

e.M., early wood; Z.w., late wood; Z. p. r., large pith ray; s. p. r., small pith ray; «;., vessel; w./., wood fiber; 

w. p.f. , wood-parenchyma fiber. Magnified 20 diameters. 

first formed often much smaller than many in the late wood (I. w.), 
which are arranged in single or double and irregular radial rows, and 
surrounded by numerous wood-parenchyma fibers. Wood fibers 
(w. /.) average 1.06 millimeters long, with very thick walls and 
small cavities; onl}^ sparingly found in early wood. Wood-paren- 
cJiyma fibers (w. p. /.) A^ery abundant in late wood, occurring in 
numerous broad tangential bands from 0.2 to 0.5 cell wide and 
extending from ray to ray as uninterrupted lines. Crystals of 
calcium oxalate very numerous. Pith rays: Large pith ra^^s (Z. p. r.) 
very numerous and from 20 to 40 cells wide and from three to five 
times as high. Crystals of calcium oxalate present. Small pith 



CHARACTERISTICS. 29 

rays (s. p. r.) only a single cell wide and from 4 to 20 cells high, 
rather inconspicuous 

6. Arizona White Oak {Quercus «n2ow>a Sargent) . (Fig. 16.) 
Heartwood dark brown or sometimes nearly black; sapwood thick 

and much lighter colored. Wood hard, very heavy, strong, close- 
grained, very durable in contact with the soil, and exceedingly 
variable in its general gross characters. Rate of growth rather slow, 
requiring from 15 to 18 years for the tree to grow 1 inch in diameter. 
Vessels (fig. 16, v.) in early wood {e. w.) 1 to 2 rows deep, round 
and from 0.2 to 0.3 millimeter in diameter, becoming abruptly 
smaller in late wood {I. w.), where they are from one-fourth to 
one-third as large as those in early wootl and of nearly uniform 
diameter. Walls of small vessels in late wood thicker than those 
of larger pores in early wood. Distribution of small pores rather 
irregular, though a slight resemblance to radial arrangement present 
in wood showing wide annual rings of growth. Wood-Jibers (w. /.) 
form bulk of late wood, but are seldom present between larger pores 
in early wood. Walls rather thick and cavities small. Lengtli 
varies from 0.71 to 1.42 millimeters with average width of O.OIS 
millimeter. Wood-parenchyma fibers {v:. p. f.) almost entirely con- 
fined to early wood, forming the bulk of the elements which compose 
the inner half of annual rings of growth. Almost entire absence of 
tangential arrangement in late wood; traces of such bands present 
in outer portion. Pith rays: Large pith rays (Z. p. r.) very numer- 
ous, from 20 to 30 cells wide, from three to four times as high and 
from 1.5 to 3.5 millimeters apart; the cells contain numerous crystals 
of calcium oxalate. Small pith rays {s. p. r.) inconspicuous, only a 
single cell wide and from 3 to 15 cells high. 

7. Post Oak {Quercus minor (Marsh) Sargent). (Fig. 17.) 
Heartwood light brown or sometimes tinged with red; sapwood 

thick and lighter colored. Wood very heavy, hard, close-grained, 
and in durability compares with that of white oak. Rate of growth 
rather slow, requiring approximately 16 years to grow 1 inch in 
diameter. 

Vessels (fig. 17, v.) in early wood {e. w.) generally 2 rows deep, 
round, and about 0.2 millimeter in diameter. In late wood (I. w.) 
nearh' uniform in size, approximately one-third as large as those in 
early wood and arranged in nearly regular radial rows of from 3 to 5 
between the large pith rays. Wood fihers (w. f.) compose major 
part of annual rings of growth. W^alls very thick, rendering the 
wood exceedingly hard and heavy. Length varies from 0.83 to 1.25 
millimeters with an average of 0.98 millimeter. Wood-parenchyma 
fibers {w. p. f.) occur sparingly in early wood. From 4 to 10 incon- 
spicuous tangential bands of average width in late wood. Pith rays: 
Large pith rays (I. p. r.) are about 25 cells wide and about four times 



30 



IDENTIFICATION OF NORTH AMEEICAN OAK WOODS. 




as high and 3 minimeters apart. Approximately 30 small rays 
(s. p. r.) only a single cell wide occur between the large rays. 

Post oak resembles white oak (Q. alba), but is distinguished from 
it by more numerous and conspicuous pith rays and smaller pores 
in the early wood. 

8. Swamp White Oak (Quercus platanoides (Lambert) Sud worth). 
(Figs. 18 and 19.) 
Heartwood light brown, sometimes slightly tinged with red; sap- 
wood ratlier thin and somewhat lighter colored. Wood very hard, 

heavy, strong and equally as du- 
rable in contact with the soil as 
white oak. R ate of growth moder- 
ately fast, requiring on an average 
about 9 years to grow 1 inch in 
diameter. 

Vessels (fig. 19, v.) in early wood 
{e. w.) from 1 to 3 rows deep ; the 
inner row usually large and ellipti- 
cal, and the succeeding rows usu- 
ally very much smaller and round. 
Large vessels from 0.2 to 0.3 milli- 
meter in diameter. In late wood 
(Z. w.) they become abruptly 
smaller and arranged in moi-e or 
less narrow, radial rows, of which 
there are frequently from ten to 
twelve between the large pith rays 
(1. p. r.). Occasionally these ra- 
dial rows originate in the middle of 
late wood and extend to the outer 
part of annual ring of growth. 
They average about 0.04 millimeter 
in diameter. Wood fibers (w. f.) 
approximately 1.04 millimeters long with tluck walls and relatively 
small cavities. Wood-parenchyma fibers {w. 'p. f.) chiefl}" confined to 
the early wood, but border small vessels in late wood. They are 
arranged in numerous, inconspicuous, tangential bands in late wood. 
Pith rays: Large pith rays {I. p. r.) are from 15 to 25 cells wide, from 
three to four times as high, and from 8 to 10 millimeters apart. Small 
rays {s. p. r.) exceedingly numerous but seldom more than 1 cell 
wide. 

Swamp white oak superficially resembles white oak {Q. alba), from 
which it is distinguished by its very light-brown color, contrasting 
more or less shar])ly with the reddish-brown color of white oak wood. 



Fig. 17. — -Post oak {Quercus minor). Transverse 
section through one entire annual ring of growth; 
€. w., early wood; I. u\, late wood; I. p. r., large 
pith ray; s. p. r., small pith ray; v., vessel; «'./., 
wood fiber. Magnified 20 diameters. 



CHARACTERISTICS. 



31 



9. Emory Oak (Quercus emoryi Torrey), (Fig. 20.) 

Heartwood dark brown or sometimes nearly black; sapwood 
rather thick and light brown, tinged with red. Wood hard, heav^', 
strong, close-grained, and not durable m contact with the soil. Wood 
of old or slow-growmg trees very brittle. Rate of growth very slow, 
requiring from 12 to 15 years to grow 1 inch in diameter. 

Vessels (fig. 20, v.) in early wood (e. w.) are from 2 to 4 rows deep 
and vary from 0.15 to 0.35 millimeter in diameter, gradually diminish- 







».Swf>i*T^Jlfefi- 



Fig. 18. 







Fig. !■ 



Fig. is.— Swamp white oak (Qmctcws platanoidcs) . Transverse section through 13 entire annual rings of 

growth. Magnified 20 diameters. 
Fig. 19.— Swamp white oak (Quercus platanoides). Transverse section through one entire ring of annual 

growth; e. «'., early wood; 1. w., late wood; I. p. r., large pith ray; «. p. r., small pith ray; v., vessel; 

w.f., wood fiber; u\ p.f., wood-parenchyma fiber. Magnified 20 diameters. 

ing in size in late wood Q,. w.), where they are 0.1 millimeter or less in 
.diameter. Small vessels arranged in regular single or rarely double 
radial rows extending to the outer part of the annual ring of growth. 
Usually two, though occasionally 1 and rarely 3 or 4 radial rows 
of small vessels between the large pith ravs. Walls of small A^essels 
thicker than those of large ones in early wood. Wood fibers iw. f.) 
on an average 1.12 millimeters long and about 0.02 millimeter wide. 
Walls tliick and the cavities very small, especially near the periphery 
of the amiual rings of growth. Wood- parenchyma fibers (w. p. /.) 
very abundant in earh^ wood and along the radial rows of small ])ores. 
Numerous single or double tangential bands in late wood. Pith rays: 
Large pith rays (I. p. r.) arc very numerous and vary from 10 to 25 



32 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



cells wide, from three to four times as high, and from 1.5 to 2.5 milli- 
meters apart; conspicuous in transverse sections. Small pith rays 
(s. p. r.) conspicuous and cells unusuall}" large compared to those of 
otlier oaks. Crystals of calcium oxalate usually confined to cells of 
large pith rays and to wood-parenchyma fibers. 

10. California Black Oak (Quercus calif ornica (Torrey) Cooper). 
(Fig. 21.) 
Heartwood bright red or tinged with yellow; sapwood thin, lighter 
colored and easily distinguished from lioartwood. Wood hard, 




Fig. -20, 



Fig. 20. — Emory oak {Quercus emoryi). Transverse section through parts of two annual rings of growth; 

e. w., early wood; I. w'., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v., vessel; w.f., wood 

fiber; j^;. p./., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 21.— California black oak (Quercus californica). Transverse section through one entire annual ring 

of growth; e. w., early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pitli ray; v., vessel; 

w.f., wood fiber; iv. p.f., wood-parenchyma fiber. Magnified 20 diameters. 

heavy, strong, though brittle, rather close-grained and not durable 
in contact with the soil. The tree requires from 12 to 15 years to 
grow 1 inch in diameter. 

Vessels (fig. 21, v.) in early wood {e. w.) from 3 to 5 rows in mod- 
erately fast-growing trees, occupying about one-fifth of the width of 
the annual ring of growth; the vessels are from 0.2 to 0.45 millimeter 
in diameter. Small vessels in late wood (J. w.) occur in single or 
double and rather irregular radial rows extending to the outer edge 
of the annual ring, usually uniform in size and measuring about 0.1 
millimeter in diameter. Wood fibers {w.f.) form the bulk of late wood 



CHARACTERISTICS. 



33 




/ / 



and are approxiinatcl}- 1.21 niillimeters long and about 0.022 milli- 
meter wide. Wood- parenchyma fibers (w. p. /.) conspicuously ar- 
ranged in irregular ,tan^0ntial bands from 2 to 6 cells wide. In early 
wood they are lilled either with starch, tannin, or crystals of calcium 
oxalate. Pith rays: Large pith rays (I. p. r.) from 10 to 30 cells wide, 
from three to five times as high, and from 2 to 3 millimeters apart. 
Small ]uth rays (s. p. r.) very clearly defined in transverse sections. 

11. White Oak {Quercus Gi6a Linnaeus). (Fig. 22.) 

Heartwood reddish brown; sapwood narrow and light colored. 
Wood very hard, heavy, strong, close-grained, and very durable in 

contact with the soil. Rate of 
growth moderately fast, requir- 
ing about 10 years to grow 1 inch 
in diameter. 

Vessels (fig. 22, v.) in early 
wood {e. w.) round, from 0.3 to 
0.5 millimeter in diameter, and 
1 row, or rarely 2 or more rows, 
deep. In late wood (I. w.) ves- 
sels abruptly diminish in diame- 
ter to approximately one-sixth 
of that in early wood, where they 
vary but little in size and out- 
line. Practically all the large 
vessels are filled with tyloses (t. ) . 
Wood fibers (w. /.) from 1 to 
1.63 millimeters long and about 
O.OIS millimeter in diameter, 
forming the bulk of late wood. 
They have very thick walls and 
consequently rather small cavi- 
ties. Wood -parenchyma fibers 
{w. p. f.) scattered irregularly 
throughout the early wood. In 
late w^ood they occur in distinct 
single or double irregular, tangential bands, varying from a few to 
many, depending upon the width of the annual rings of growth. 
Pith rays: Large pith rays (I. p. r.) are from 10 to 40 cells w^ide, and 
from three to five times as high, and approximately 0.4 millimeter 
apart. Small pith rays (s. p. r.) usually 1 cell wide, though some 
rays are from 2 to 3 cells wide and from a few to 20 cells high. 

The wood of white oak is readily distinguished from that of red 
oak by the fact that the pores in the late wood diminish abruptly in 



Vft 




Fig. 22.— White oak {Quercus alba). Transverse sec- 
tion through one entire annual ring of growth; e. w., 
early wood; I. w., late wood; I. p. r., large pith ray; 
s. p. T., small pith ray; v. vessel; w. /., wood fiber; 
w. p.f., wood-parenchyma fiber; t., tyloses. Magni- 
fied 20 diameters. 



34 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



tlie former, while in the hitter they diminish gradually in size. 
Another character helpful in separating these two species is the pres- 
ence of tyloses within the pores of white oak and their absence in 
those of the red oak. 

White oak wood may be confused with the wood of bur oak (Q. 
macrocarpa), swamp white oak (Q. platan oide s) , post oak (Q. minor), 
chestnut oak {Q. prinus), cow oak (Q. micJiauxii), chinquapin oak 



ar 




Fig. 23 



Fig. 23.— Bur oak {Quercus macrocarpa). Transverse saction through three entire aiinaal rin,c;s of growth; 
a. r., annual ring. Magnified 20 diameters. 

Fig. 24.— Bur oak {Quercus macrocarpa). Transverse section through one entire annual ring of growth; 
e. w., early wood; /. «,'., late wood; /. p. r., large pith ray; s. p. r., small pith ray: v., vessel; r. r., radial 
row; w.f., wood fiber: ir. p.f., wood-parenchyma filipr: /., tyloses. Ma'ini.'ied 20 diameters. 

{(}. acnminata), and overer.p oak (Q. lyrata). See special distinctions 
under each. 

12. Bur Oak (Quercus macrocarpa Micliaux). (Figs. 23 and 24.) 

Ileartwood dark, rich brown in color; sapwood thin and much 
lighter in color. Wood hard, heavy, very strong and tough, close- 
grained, and not liable to warp or check. Lumber never distin- 
guished from white oak (Quercus cdha) on the market. The most 
valuable timber of the American oaks. 

This oak has the power to adapt itself to great variation of soil 
and climatic conditions, which enables it to live from Maine to 
Manitoba and southwest to Texas. The character of the wood pro- 
duced under favorable conditions varies considerably from tliat pro- 
duced near the limits of its botanical distribution. Illustrations of 



CHARACTERISTICS. 35 

transverse sections of different samples of wood are here shown. 
Figure 24 shows a transverse section of wood collected in southern 
Indiana, where tlie bur oak attains its largest size and greatest value; 
the wood from which figure 23 was made was collected in north- 
western Minnesota, where this species approaches the chaparral form 
and consequently has very narrow annual rings of growth (fig. 23, 
a. r.). 

Bur oak may often be distinguish-ed from white oak by its wider 
radial rows of small vessels (fig. 24, r. r.) in late wood (J. w.). In 
white oak small pores often form a single narrow and rather regular 
row between the large pith rays (/. p. r.); while in the bur oak they 
are scattered in several rather wide bands bordered by wood-paren- 
chyma fibers {v\ p. f.), which often renders the wood somewhat 
lighter than that of white oak. Tangential bands of wood-paren- 
chyma fibers are more conspicuous in bur oak. The wood fibers 
(w.f.) average about 1.35 millimeters long and 0.021 millimeter in 
diameter. Large pith rays (I. p. r.) are about 6 millimeters apart. 

13. Durand Oak (Quercus hreviloha (Torrey) Sargent). (Fig. 25.) 
lleartwood small and brown in color; sa})wood thick and much 

lighter colored. Wood moderatel}" hard, rather light, though brittle, 
and in general appearance resembles white oak; not durable in 
contact with the soil. Rate of growth very slow, especially near its 
limits of distribution, requiring approximately 15 years to grow 
1 inch in diameter. 

Vessels (fig. 25, v.) in early wood (e. id.) oval and generally only a 
single row deep; generally contain considerable tyloses {t.). Small 
vessels in late wood (Z. iv.) surrounded by wood-parenchyma fibers 
(«\ p.f.); they diminish in size abruptly and form broad radial rows 
(/'. /'.) which widen or become branched as they approach the periphery 
of the annual ring of growth (a. r.). Wood fibers (w.f.) chiefly occur 
in groups scattered tlirough the late wood. They are 1.23 millimeters 
long, vv'hich is only slighth' shorter than those of white oak. Walls 
thick and cavities small. Wood-parenchyma Jihers highly developed 
and largely confined to late wood, rendering the wood among the 
liglitest of the eastern oaks. Pith rays: Large pith rays (1. p. r.) 
from 10 to 30 cells wide and from three to four times as high. Distance 
between the large rays varies exceedingly in different parts of the 
same specimens. They are more numerous in this species, however, 
than in wb.it e oak. Small pith rays (s. p. r.) numerous but incon- 
spicuous, only a single cell wide and from a fev,' to 20 or more cells 
high. 

14. Willow O&k (Quercus pheUos 'Linnseus). (Fig, 26.) 
lleartwood reddish brown, sometimes tinged with yeUow; sapwood 

thin and much lighter colored, though sometimes slightly tinged 



36 



IDENTIFICATION OF NORTH AMEEICAX OAK WOODS. 



with red. Wood moderately hard, heavy, strong, rather cross- 
grained, and moderately durable in contact with soil. Rate of 
growth usually rather slow, requiring from 10 to 15 years to grow 
1 inch in diameter. 

Vessels (fig. 26, v.) in early wood (e. w.) are elliptical or oval in 
outline, with an average radial diameter of from 0.25 to 0.4 milli- 
meter ami tangential diameter of from 0.2 to 0.3 millimeter. Usually 




Fig. 25. 



Fig. 2G. 



Fig. 25.— Durand oak (Quercus hrcviloha). Tranverse section through three entire annual rings of growth; 

a. r., annual ring; e. w., early wood; I. w., late wood; /. p. r., large pith raj-; s. p. r., small pith ray; v., 

vessel; r. r., radial row; «'./., wood fiber; w. p./., wood-parenchyma fiber; /., tyloses. Magnified 20 

diameters. » 

Fig. 26. — Willow oak {Quercus pheUos). Transverse section through one entire annual ring of growth; 

e. w.. early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v., vessel; w.f., wood 

fiber; w. p.f., wood-parenchyma filDer; /., tyloses. Magnified 20 diameters. 

only a single row of vessels within an annual ring of slow growing trees 
and chiefly filled with tyloses {t.); in fast growing trees usually from 
2 to 3 rows, abruptly diminishing in size in late wood {I. id.). Small 
vessels often laterally compressed and irregular in outline and 
arranged in 2 or 3 rather conspicuous radial rows between the large 
pith rays. Wood fibers (w.f.) 1.52 millimeters long and 0.021 milli- 
meter wide. They are seldom found to any great extent in early 
wood, but form the bulk of elements in late wood between the radial 
rows of small vessels and entirely surrounded by wood-parenchyma 
fibers. Wood-parenchyma fibers (w. p. f.) are confined chiefly to 
early wood and bordering the small vessels in late wood. The 
tangential bands of wood-parenchyma f.bers, so common in most 



CHARACTERISTICS. 37 

oaks, occur veiy sparingly in the wood of this species. There are a 
few short bands or groups of these elements, but usually they can 
be distinguished only under the microscope. Pitli rays: Large pith 
rays (i. p. r.) from 10 to 30 cells wide, and from two to four times as 
high, and from 2 to 3 millimeters apart. Small rays (s. f. r.) are, as 
a rule, only a single cell wide, and from a few to 20 cells high. 

The wood of willow oak, frequently confused with that of shingle 
oak {Q. imbricaria) , is distinguished by having less porous early wood 
than the latter, while the pores in the early wood of willow oak are 
usually elliptical, those in the shingle oak being round. 

15. Overcup Osik (Quercushjrata Walter). (Fig. 27.) 
Heartwood dark brown and easily distinguished from the thick 

lighter-colored sapwood. Wood moderately hard, rather heavy, 
strong, and very durable in contact with soil. In its general appear- 
ance, physical characteristics, and rate of growth it is similar to white 
oak. 

Vessels (fig. 27, v.) in early w^ood (e. w.), 2 to 3 rows deep; and, as 
well as the smaller pores in late wood (l. w.), are slightly compressed 
laterally. They are abruptly smaller in diameter in late wood, 
forming broad and often rather irregular, radial bands surrounded by 
conspicuous and thin-walled w^ood-parenchyma fibers (r. r.). lloofZ 
fihers (w. f.) are 1.32 millimeters long and 0.022 milHmeter in diam- 
eter, and less numerous than those of white oak; their walls are 
usually somewhat thinner. Wood-par encliyTna fibers (w. p. f.) 
arranged in clearly defined tangential bands in late wood. The 
number of these bands varies with the width of the annual rings of 
growth. Pith rays: Large pith rays (Z. p. r.) are from 15 to 40 milh- 
meters wide and from three to five times as high. Small rays (s. p. r.) 
are only a single cell wide and from a few to 20 or more cells high. 

Overcup oak wood, sometimes confused with white oak (Q. alba), 
is readily distinguished from the latter by its larger and more niuner- 
ous pores in the early wood. 

16. Cow Oak (Quercus micha.uxii Nuttall). (Fig. 28.) 
Heartwood light brown or somewhat tinged with red; sapwood 

thin and somewhat darker colored. Wood hard, heavy% tough, 
close-grained and durable in contact with soil. Under favorable 
conditions cow oak requires from 8 to 10 years to grow 1 inch in 
diameter. In the form of lumber it is seldom distinguished from 
white oak. 

Vessels (fig. 28, v.) in early wood (e. w.) from 2 to 3 rows deep, and 
approximately 0.5 millimeter in radial and 0.4 millimeter in tangen- 
tial diameter. In late wood (?. w.) small vessels arranged in 3 to 5 
radial rows, which gradually widen or become branched near the 
periphery of annual rings of growth. Wood Jibers (w. f.) are thick 
walled and on an average 1.54 millimeters long and 0.021 milHmeter 



38 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



wide. They form the bulk of the elemeuts in kite wood. Wood- 
parencliyma fibers {w. p.f-) are confined chiefly to early wood, but also 
surround the smaller vessels in late wood. Narrow, irregular, tan- 
gential bands of wood-parenchyma fibers occur in the outer part of 
late wood. Pith rays: Large pith rays (I. p. r.) are from 20 to 40 
cells wide and from one to three times as high. Small rays (s. p. r.) 
are exceedingly numerous and are only one cell wide and from a few 
to 20 or more cells high. 

Cow oak wood, whicli resembles white o:i!: {Q. alba) more closc^ly 
than that of any other species, is lighter colored end generally has 




Fig. 27. Fig. 2S. 

Fig. 27.— Overcup oak {Quercus lyrala). Transverse section through one entire annual ring of growth; 
e. w., early wood; I. uk, lale wood; I. p. r., large pith ray; s. p. r.. small pith ray; v., vessel; r. r., radial 
row; !«./., wood fiber; w. p. f., wood-parenchyma fiber; f., tyloses. Magnified 20 diameters. 

Fig. 28.— Cow oak {Quercus mkhauxii) Transverse sectioa through a portion of two annual rings of growth; 
e. «,'., early wood; /. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v., vessel; r. r., radial 
row; u\f., wood fiber; tv. p.f., wood-parenchyma fiber; /., tyloses. Magnified 20 diameters. 

less conspicuous tangential ])ands of wood-parenchyma fibers in the 
late wood than white oak. 

17. Chestnut Oak (Quercus prinus Linnteus). (Fig. 29.) 

Heartwood yellowish or reddish brown and sharply defined from 
the lighter and slightly reddish, narrow sapwood. Wood hard, hea^s^^, 
strong, tougli, moderately close-grained and durable in contact with 
soil. Rate of growth is low, requirmg from 12 to 20 years for the 
tree to grow 1 inch in diameter. 

Vessels (fig. 29, v.) round or elliptical in early wood (e. w.) and from 
3 to 5 rows deep. Small vessels in late wood (?. w.) often polygonal 



CHARACTERISTICS. 



39 



and sometimes so small that their diameters hardly exceed those of 
wood-parenchyma fibere. Radial rows (/'. r.) of small vessels are 
wavy or slightly branched, and surrounded by numerous wood- 
parenchyma fibers which form narrow tangential bands (lo. p. f.) in 
late wood. Wooffhers (^v.f.) compose the bulk of late wood and are 
about 1.31 millimeters long and 0.020 millimeter wide, with thick 
walls and rather small cavities. Wood-jiarenchyma fhers (w. p. f.) 
are scattered in isolated groups in early wood. In late wood they 
occur in regular or branched and uninterrupted tangential bands which 
can be readily seen with the unaided eye. Pith rays exceedhigly 
numerous and constitute about 
one-fifth of the cellular sub- 
stance of the wood. Large pith 
rays (/. p. r.) are often 20 to 30 
cells wide and from three to six 
times as high. Small pith rays 
(s. p. r.) only one cell wide and 
from 4 to 15 cells high, appear- 
ing as long, well-defined lines in 
transverse sections. 

The wood of chestnut oak is 
sometimes mistaken for white 
oak (Q. alba), but it is distin- 
guished from the latter by its 
more prominent pith rays and 
the lack of a faint reddish tinge 
present in the wood of white 
oak. 

18. Chinquapin Oak (Qiiercus- 

a c u m i nata (Mi c h a u x ) 

Houba). (Figs. 30 and 31.) 
Heartwood light brown or 
slightly tinged with red; sa])- 
wood thin and lighter colored. 
Wood hard, heavy, strong, and 
close-grained. Its durability and 
chestnut oak. 

Vessels (fig. 30, v.) in early wood (e. w.) round or sometimes elUptical 
and from 0.15 to 0.35 millimeter in diameter; seldom formmg con- 
tinuous rows, but are generally arranged in groups of 2 to 5 vessels 
deep (fig. 31) between the large pith rays. Small pores in late wood 
(Z. w.) are about one-third as large as those of early wood, and with 
very thick walls compared w^ith those of the large pores which are 
usually filled with tyloses (fig. 30, t.). They are arranged in 3 to 5 




ev/ 



Sp.T' Lp.T 

Fig. 29. — Chestnut oak {Qucrcus prinus). Transverse 
section through one entire annual ring of growth; 
f. w., early wood; I. «'.. late wood; I. p. r., large pith 
ray; s. p. r., small pith ray; v., vessel; r. r., radial 
row; u'.f., wood fiber; w. p. /., wood-parenchj-ma 
fiber. Magnified 20 diameters. 

rate of p;rowth similar to that of 



40 



IDENTIFICATION OF NORTH AMEEICAN OAK WOODS. 



rather irregular radial rows which extend to the periphery of the 
annual ring of growth where they are exceedingly small. Wood 
fibers (fig. 31, w. /.) composed mainly of thick-walled elements of 
about 1.15 millimeters in length. In very narrow annual rings of 
growth, such as are usually found near the periphery of the stem of 
old trees, the bulk of the wood substance consists of large vessels, 
wlule the remainder is mostly composed of thin-walled wood-paren- 
chyma fibers, which render the wood light and brittle. Wood- 
parenchyma f hers (fig. 31, w. p. f.) in early wood highly developed 



spr' 





Fig. ?a. 



Fig. 30. — Chinquapin oak {Quctcus acuminata). Transverse section through four entire annual rings of 
growth; e. w., early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; r., vessel; t., 
tyloses. Magnified 20 diameters. 

Fig. 31. — Chinquapin oak (Quemis acuminata). Transverse section through one entire annual ring of 
growth; v., vessel; «''./., wood fiber; tc. p.f., wood-parenchyma fiber. Magnified 20 diameters. 

and scattered among the vessels. In late wood these fibers are 
found most abundantly near the small pores, and also in irregular 
and interrupted tangential bands. Pith rays: Large pith rays (fig. 
30, Z. p. r.) from 10 to 35 cells wide, and from three to four times as 
high and about 3 millimeters apart. Numerous small pith ra3's 
(fig. 31, s. p. r.) only a single cell wide and from 3 to 15 cells high. 

Chinquapin oak is often sold as white oak {Q. alba) and is used for 
the same purposes, but it resembles chestnut oak {Q. jJnniis) more 
closely than it does white oak. It is distinguished from white oak 
b}' its dark-brown color, which contrasts more or less sharply with 
the reddish-brown tinge of the latter. The narrow amiual rmgs of 



CHARArTERTSTTC'ri. 41 

growth and the proportionately larger amount of early wood than 
late wood of chmqiiapm oak will usually serve to separate it from 
chestnut oak. 

19. Shingle Osi^ (Quercus imhricariaMivhiiux). (Fig. 32.) 
Heartwood light brown and slightly tinged with red; sapwood 

although somewhat lighter in color is not clearly distinguished from 
the heartwood. Wood hard, heavy, close-grained and rather tough. 
Rate of growth moderately fast, requiring from 10 to 12 years to 
grow 1 inch m diameter. 

Vessels (fig. 32, v.) in early wood {e. w.) occupy about one-half of 
the annual rings of growth. Large vessels from 3 to 6 rows deep 
and are more or less uniform in size and usually contain tyloses {t.). 
Their average radial diameter about 0.35 millimeter and tangential 
diameter about 0.25 millimeter, although in general outline the pores 
vary from round to elliptical or oval. In late wood (I. w.) t\\&j are of 
uniform size and only about one-eighth as large as those in early wood, 
and arranged in 2 or 3 single or double conspicuous radial rows. 
Wood fibers {w. /.) on an average 1.03 millimeters long and 0.017 
millimeter wide and chiefly found between radial rows of small pores 
and wood-parenchyma fibers in late wood. Less than one-fifth of all 
the wood elements within annual rings of growth consist of wood 
fibers. Wood-parencJiyma fibers (w. p.f.) conspicuous in late wood, 
and form the bulk of elements surrounding the radial rows of small 
vessels. They branch out from these rows into tangential bands 
that can be readily seen with the unaided eye. There are from 8 to 
1 2 of these bands to each annual ring of growth. Pith rays: I^arge 
pith rays (Jt. p. r.) from 15 to 40 cells wide and from two to four times 
as high. Small pith rays {s. p. r.) inconspicuous and, as a rule, only 
a single cell wide, and from 5 to 20 cells high. 

(See descri])tion under Willow oak {Q.. pheUos) for possible confusion 
with the wood of sliingle oak.) 

20. Water Oak (Quercus nigra Linuiieus). (Fig. 33.) 
Heartwood light brown tinged with yellow; sapwood rather 

thick and lighter colored. Wood hard, rather close-grained and 
not durable in contact with soil. Rate of growth moderately fast, 
requiring from 10 to 12 years to grow 1 inch in diameter. 

Vessels (fig. 33, v.) in early wood (e. w.) arranged in from 1 to 3 
tangential rows. Their tangential diameter varies from 0.14 to 
0.28 millimeter and radial diameter from 0.16 to 0.35 millimeter. 
Vessels diminish gradually in size in late wood (J,, w.), where they are 
aiTanged in 2 or 3 single or double radial rows, extending to the 
periphery of the annual rings of growth. The average diameter of 
the small pores is about 0.05 millimeter. They are circular and 
have very tliick walls. V/ood ^bers (w. f.) vary in length from l.OS 



42 



IDENTTFICATION OF NORTPI AMERICAN OAK WOODS. 



to J.IK) millimeters, with an average length of 1.43 millimeters. 
Their walls are very thick and cavities small, forming the hard 
tissue between the radial rows of small vessels in late wood. The 
masses of hard fibers are intersected by very many small pith rays 
and by single or double tangential bands of wood-])arenchyma 
fibers. Wood-parencliyma Jihers (iv. p. /'.) very abundant both in 
early and late wood, and in the latter are arranged in numerous 
tangential bands, wliich are easily see^i with a pocket lens. There 
are from 5 to 15 of these bands in late wood, depending upon the 




^'lp7 ^V^ 




Fi(,. .« 



SP^-- Fig. 32. 

Fig. .32.— Shingle oak {Quercus iinbricaria). Transverse section through one entire annnal ring of growth; 

f. w., early wood; 1. w., late wood; 1. p. r., largo pith ray; s. p. r., small pith ray: r.. vessel; w. /.. wood 

fiber; u\ p./., wood-parenchjTna fiber; t., tyloses. Magnified 20 diameters. 
Fig. .3.3.— Water oak (Qucrciis nigra). Transverse section through one entire annual ring of growth; r. u\, 

early wood; 7. ?/'., late wood; ?. p. r., large pith ray; s. p. r., small pith ray; v.. vessel; »•./., wood fiber; 

M'. p. /., wood-parenrhjTna flijer. Magnified 20 diameters. 

width of the annual rings of growth. Pith rays: Large pith rays 
(?. p. r.) from 15 to 40 cells wide, from tlu"ee to four times as liigh, 
and from 3 to 5 millimeters apart. The small pith rays (s. p. r.) 
are conspicuous, but only 1 cell wide and from 5 to 20 cells high. 

21. Turkey O&k (Quercus cateshsei Michaux) . (Fig. 34.) 

Heart wood light brown tinged with red or yellow; sap wood tliick 
and somewhat lighter colored, though occasionally quite yellowish. 
Wood rather hard, heavy, medium close-grained and not very dura- 
ble in contact with the soil. Tliis species usually grows in dry 
uplands, where the rate of diameter increase is moderately slow, 
rcHpiiring from 10 to 15 years to grow 1 inch in diameter. 



CHAKACTERISTICS. 



43 



Vessels: Large vessels (fig. 34, v.) in early wood (r. lo.) from 1 to 3 
rows deep, varying in diameter from 0.26 to 0.40 millimeter, but 
gradually diminishing in size toward the periphery of the annual 
ring of growth. Vessels in late wood (/. w.) vary from 0.10 to 0.20 
millimeter in diameter and have very thick walls compared with 
those in early wood. There are from 1 to 3 irregular, interrupted 
radial rows of small pores between the large pith rays. Wood 
fibers (w. /.) tliick-walled and almost entirely confined to late wood, 
where they are scattered in small groups. Wooclfhers on an average 





Ipf 



Fig. 34. 



Ipr -' 



Fig. 3.5. 
Fig. 34. — Turkey oak (Quercus catesbxi). Transverse section through parts of two annual rings of growth; 

e. w., early wood; I. w., late wood; /. p. r., large pith ray; s. p. r., small pith ray; v., vessel. Magnified 

20 diameters. 
Fig. 35.— Spanish oak (Quercus digitata). Transverse section through one entire annual ring of growth; 

e. te., early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v. vessel; w.f., wood 

fiber; w. p. /., wood-parenchyma fiber. Magnified 20 diameters. 

1.47 millimeters long and about 0.026 millimeter wide. Wood- 
imrencliyma fibers abundant both in early and late wood, in the 
latter surrounding the smaller vessels and forming irregular, incon- 
spicuous, and much interrupted tangential bands. Usually from 6 
to 10 of these bands within an annual layer of growth. Pith rays: 
Large pith rays (I. p. r.) from 20 to 45 cells wide, from two to four 
times as high, and from 2 to 4 millimeters apart. Cells in the small 
pith rays {s. p. r.) are large and the rays themselves quite conspicuous. 

22. Spanish Oak {Quercus digitata (Marsh) Sudworth). (Fig. 35.) 

Heartwood reddish; sap wood thick and lighter colored, with a 
slightly brownish tinge. Heartwood resembles that of red oak, 
except that it is tinged brighter red. It is light in weight, though 



44 IDENTIPTCATTON OF NORTH AMERICAN OAK WOODS. 

moclorately hard and strong, not durable in contact witli the soil, 
and moderately fast gi-owing, recjiiiring approximately 8 years to 
grow 1 inch in diameter. 

Vessels (fig. 35, v.) in early wood {e. w.) form a single interrupted 
row. They are elliptical or oval and vary from 0.15 to 0.25 milli- 
meter in diameter. Small pores on an average about 0.075 milli- 
meter in diameter, becoming smaller in late wood (/. iv.), where they 
form single radial and nearly parallel rows extending through the 
annual rings of growth. Wood Jihers (w.f.) very nmnerous in early 
wood, where they occur in small groups among the thinner-walled 
elements and gradually increase in number in late wood. In trans- 
verse section the}" are pentagonal in outline and have moderately 
tluck walls and small cavities. The individual fibers vary from 1.08 
millimeters to 2 millimeters in length, with an average width of 0.024 
millimeter. The wood of this species contains fibers having the 
greatest average length (1.65 millimeters). Wood-parendtyma Jibers 
{w. p. /.) arranged in concentric lines around the vessels in early 
wood and bordering the small pores in late wood. They also form 
irregular, narrow tangential bands in late wood. There are from 10 
to 12 of these bands in annual rings of growth of moderately fast- 
growing trees. Pith rays: Large pith rays (I. p. r.) on an average 
about 20 cells wide and from two to three times as high, and from 2 
to 4 millimeters apart. The height and width of the rays vary con- 
siderably, depending upon the age and size of the trees. Small pith 
ra3^s (s. p. r.) are numerous, and usually only 1 cell wide and from 
8 to 16 cells high. 

The wood of Spanish oak is occasionally confused with red oak 
{Q. rubra), but is distinguished by having fewer and less-pronounced 
pith rays than red oak. 

23. Blackjack Odik {Quercus 7na,rila,ndica^l\\eYic\\\\.). (Fig. 36.) 

Ileartwood dark brown; sap wood somewhat lighter colored and 
with a yellowish tinge. Wood hard, heavy, and not durable in con- 
tact with soil. Rate of growth comj^ares mtli that of post oak. 

Vessels (fig. 36, v.) in early wood (e. w.) usually 4 rows deejD and 
invariably filled with tyloses it.), round or seldom elliptical m outline 
and varying from 0.2 to 0.4 millimeter in diameter. Vessels in late 
wood (L ID.) about one-sixth as large as those in early wood, and 
arranged in irregular or branched radial rows. Small pores uniform 
in size with very thick walls. Wood fibers (w.f.) have veiy thick 
walls and rather small cavities. They vary from 1.04 to 1.63 milli- 
meters in length, with an average length of 1.38 millimeters, and are 
approximately 0.027 millimeter wide. Wood- parenchyma fibers {w. 
p. f.) are scattered in short, irregular, tangential bands or in small 
groujxs in late wood and surroimding the large and small vessels. 



CHAKACTESISTICS. 



45 



In radial section these elements may be seen with, the aid of a micro- 
scope in distinct parallel lines. Pith rays: Large pith rays (Z. p. r.) 
from 10 to 40 cells wide and from two to four times as high. Rays 
in the wood of trees grown in dry upland are more higldy developed 
than those in wood grown in rich moist lowlands. Small pith rays 
{s. J), r.) are exceedingly numerous and usually only one cell wide, 
occasionally 2 or 3, and from 10 to 20 cells high. 




7! 



-tpr 




Fig. 3G. 



Fig. 37 



Fig. 3G. — Blackjack {Qucrcus marilandica). Transverse section through one annual ring of growth; r. v., 

early wood; I. w., late wood; 1. p. r., large pith ray; s. p. r., small pith ray; r., vessel; w.f.. wood fiber; 

tv. p. /., wood-parench>^lla fiber. Magnified 20 diameters. 
Fig. 37. — Scarlet oak (Quercus coccinea). Transverse section tlirough two entire annual rings of growth; 

e. w., early wood; I. tc, late wood; I. p. r., large pith ray; s. p. r., small pith ray; t'., vessel; «'./., wood 

fiber; «'. p./., wood-parenchyma fil)er. Magnified 20 diameters. 

24. Scarlet Oak (Quercus coccinea Muenchh.). (Fig. 37.) 

Heart wood reddish brown or slightly tinged with yellow; sap wood 
thick and much lighter colored. Wood hard, heavy, and tough and 
in its general properties and rate of growth compares with that of 
yellow oak. Approximately one-half of the annual ring of growth 
consists of early wood. 

Vessels (fig. 37, v.) in early wood (e. iv.) form a conspicuous ring 
from 3 to 5 rows deep. They are either round, elliptical, or oval 
and are from 0.2 to 0.4 millimeter in diameter; gradually diminishing 
in size in late wood (I. w.). In late wood they are arranged in smgle 
though more or less irregular radial rows, visible with a pocket lens 
or even wdth the unaided eye when perfectly smooth sections are 



46 IDExXTIFICATIOK OF NORTH AMERICAN OAK WOODS. 

prepared. Walls of vessels in late wood are very thick, averaging 
0.05 millimeter. There are from 2 to 4 conspicuous radial rows of 
small vessels between the large pith rays. Wood fibers (iv. f. ) are 
almost entirely wanting in early wood. They form a rectangular 
grouj) in late wood between the radial lines of small vessels and tan- 
gential bands of wood-parenchyma fibers. They have an average 
length of 1.49 millimeters and are approximately 0.023 millhneter 
wide. The longest individual fiber was found in the wood of this 
species, measuring 2.08 millimeters. Wood-parenchyma fibers (uk P-f-) 
are arranged principally in numerous tangential bands in late wood, 
where there are from 5 to 15 of such rows within an annual layer of 
growth of average width. Pith rays: Large pith rays (L p. r.) are 
about 30 cells wide and from three to four times as high. Small pith 
rays {s. p. r.) only a single cell wide and vary in height from several 
to 12 or 15 cells. 

Scarlet oak is often mistaken for yellow oak (Q. velutina), from 
which it can be recognized by its more or less reddish tinge, yellow 
oak having a yellowish tinge. Scarlet oak wood is sometimes con- 
fused also with red oak (Q. rubra), from which it is distinguished by 
its more pronounced reddish color and narrow annual rings of growth, 
red oak wood liavmg a pale red tinge and wide rings of growth. 

25. Bluejack Oak (Quereus hrevifolia Sargent). (Fig. 38.) 
Ileartwood liglit brown and occasionally tinged with red; sapwood 

thick and dark brown and easily distinguished from the heartwood. 
Wood hard, strong, moderately close-grained, and not durable in 
contact with the soil. 

Vessels (fig. 38, v.) in early wood {e. w.) from 0.15 to 0.25 milli- 
metei' in diameter. They are from 3 to 5 rows deep and much 
interrupted, giving the ap])earance of a succession of gi'ou])s of vessels. 
Vessels diminish in size to less than 0.05 millimeter in diameter 
in late wood (L w.), forming from 3 to 5 irregular radial rows and 
having thicker walls than those in early wood. Wood fibers (w. f.) 
have an average length of 1.12 millimeters. They are not abundant 
ill early wood, but form the bulk of the elements between the radial 
rows of small vessels in late wood. Wood-parenchyma fibers (tv. p. f.) 
abundant both in early and late wood. They surround the large 
and small vessels, and in late wood occur in numerous, inconspicuous, 
irregular tangential bands. Pith rays: Large pith rays (L p. r.) 
are from 15 to 40 cells wide, from three to four times as high and 
1 to 4 millimeters apart. Small pith rays {s. p. r.) are conspicuous 
in transverse sections, though seldom more than 1 cell wide and 
from 10 to 20 cells high. 

26. Pin Oak {Quereus palustris Mlienchh.). (Fig. 39.) 
Heartwood dark brown tinged with red ; sapwood somewhat lighter, 

though occasionally slightly darker in color than the heartwood = 



CHARACTERISTICS. 



47 



Wood hard, heavy, tough, and coarse-gramed. Rate of growth and 
durabihty similar to that of willow oak. 

Vessels (fig. 39, v.) in early wood (e. w.) arranged in rather small 
groups between the large pith rays, and numbering from 6 to 12, 
nearly round pores, to each group; pores from 0.15 to 0.25 milli- 
meter in diameter. Small pores in late wood (J. w.) occur in rather 
irregular, interrupted radial rows, which originate near the middle 
of the late wood and extend to the periphery of the annual ring of 
growth. There are usually 3, but occasionally from 5 to 7, radial 




Fig. 39. 



Fig. 38.— Bliiejack oak (Quercus hredfoUa). Transverse section through one entire aiiuual ring of growth; 

f. ii'., early wood; ?.»■., late wood; /. p. r., large pith ray; s. p. r., small pith ray; v., vessel; w./., wood 

fiber; tv. y.f., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 39. — Pin oak {Quercus palustris). Transverse section through one entire annual ring of growth; e. w., 

early wood; I. w., late wood; I. p. r., large pith ray; s. p. r., small pith ray; v., vessel; «'./., wood fiber; 

w. p.f., wood-parenchyma fiber. Magnified 20 diameters. 

rows of small pores between the large pith rays. Wood fibers {w. f.) 
in early wood very sparse, but they form the bulk of the late wood. 
They are about 1.35 millimeters long and 0.017 millimeter wide. 
The cell walls are usually quite thin. Wood-parenchyma fibers 
(w. p.f.) abundant both in early and late wood. In the latter they 
are arranged in numerous distinct narrow bands, depending upon the 
width of the annual rings of growth. Pith rays: Large pith rays 
(Z. p. r.) are from 0.25 to 0.5 millimeter wide, from 7 to 15 millimeters 
high, and from 2 to 3 millimeters apart. Small pith rays (.<?. p. r.) 
numerous, only a single cell wide and from 10 to 20 cells high. 



48 IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 

Pin-oak wood is very similar in general appearance to red oak 
(Q. rubra) and from which it can be distinguished only with difficulty. 
The pores of ])in oak are less numerous and often considerably 
smaller than those in red oak. 

27. Texan Oak (Quercus texona Buckley). (Fig. 40.) 

Heartwood reddish brown, closely resembling that of red oak; 
sapwood light and sometimes tinged with yellow. Wood hard, 
heavy, close-grained, moderately tough and not durable in contact 
w4tli soil. Rate of growth equal to that of Spanish oak. 

Vessels (fig. 40, ik) in early w^ood (e. w.) numerous and usually 
from 3 to 5 (rarely 2) rows deep. They are round or slightly com- 
pressed tangentially, and are from 0.15 to 0.3 millimeter in diameter, 
varying but little in size between the inner and outer rows. Pores 
are abruptly smaller in late wood (Z. w.), being less than one-third 
as wide as those in early wood and having quite thick walls. They 
are arranged in fi'om 2 to 4 single or double radial rows extending 
to the periphery of the annual ring of growth. Wood fibers {w. f.) 
arc confuied almost entirely to late wood, where they form dense 
masses between the radial rows of small vessels. They average 
about 1.37 millimeters long and approximately 0.023 millimeter 
wide, and have thick walls and small cavities. Wood-parencJiyma 
fbers {w. p.f.) abundant in early wood, where they occur in numerous 
irregular, interrupted, tangential bands surrounding the vessels. 
Crystals of calcium oxalate very numerous in these elements. Pith 
rays: Large pith rays (1. p. r.) are from 20 to 30 cells wide, from three 
to four times as high and about 3 millimeters apart. Small rays 
(s. p. r.) conspicuous, but they are seldom more than 1 cell wide 
and from 5 to 18 cells high. 

The wood of Texan oak is the chief substitute for red oak {Q. rubra) 
and it is difficult to distinguish from the latter species. A slight 
yellowish tinge of Texan oak and its narrow annual rings of growth 
will usuall}" serve to separate it from the red oak. 

28. Yellow Oak {Quercus velutina, Lamarck). (Fig. 41.) 
Heartw^ood reddish brown or tinged with yellow; sapwood thin 

and almost white. Wood moderately hard, heavy, quite strong, 
rather coarse, straight-grained and not durable in contact with the 
soil. Rate of growth moderately slow, requiring from 12 to 14 
years to grow 1 inch in diameter. 

Vessels (fig. 41, v.) in early wood {e. w.) from 3 to 5 rows deep, 
and elli])tical in shape, being fi'om 0.2 to 0.5 millimeter in tangential 
and from 0.3 to 0.7 millimeter in radial diameter. They gradually 
diminish in size in late wood (/. w.), forming single irregular radial 
rows of vessels about 0.06 millimeter in diameter. Occasionally 
these radial rows do not reach the periphery of the annual rings of 



CHATiA('TERTSTTrS. 



49 



growth. Woodjihers {w. f.) compose the bulk of the elements m late 
wood and average 1.3 millimeters long and 0.022 wide. ^Vood- 
farencliy ma fibers (w. l^.f.) abundant in late wood and are arranged in 
concentric lines around the large and small vessels. These can best 
be seen in radial sections as distinct uninterrupted parallel lines. 
Such fibers also arranged in numerous single and much interrupted 
tangential bands or in isolated groups which are not conspicuous 
on a transverse section. Pith rays: Large pith rays (I. p. r.) are 
from 20 to 40 cells wide, from two to four times as high and on an 




P ''Pf 



Fig. 40 



Fig. 40. — Texan oak {Quercus texana). Transverse section through one entire annual ring of growth; e. w., 

early wood; Z.m'., late wood; /. p. r., large pith ray; s. p. r., small pith ray; v., vessel; ?/'./., wood fiber; 

w. p. f., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 41.— Yellow oak (Quercus velutina). Transverse section through parts of two annual rings of growth; 

e.w., early wood; Z.w., late wood; L p. r., large pith ray; s. p. r., small pith ray; r., vessel; m\/., wood 

fiber; w. p.f., wood-parenchyma fiber. Magnified 20 diameters. 

average of 3 millimeters apart. Small pith rays (s. p. r.) are from 
1 to 3 cells (rarely more than 1 cell) wide and from 3 to 18 cells high. 
For possible confusion of this wood with scarlet oak {Q. coccinea) 
see description of the latter. 

29. Red Oak (Quercus rubra Ijinnseus) . (Fig. 42.) 

Heartwood light red or slightly' tinged with, brown; sapwood tliin 
and lighter colored. Wood hard, heavy, moderately strong, close- 
grained, and not durable in contact mth soil. Tliis is among the 
fastest-growing oaks, increasing in diameter at the rate of 1 inch 



50 



TDENTTFICATION OF NORTH AMERICAN OAK WOODS. 



in about 8 or 10 years. Next to wliite oak, this is the most common 
oak on the market in the form of manufactured himber. It is exten- 
sively used in the manufacture of furniture and for interior finish. 
The ''silver grain" (large pith rays) is very conspicuous when the 
logs are quarter-sawed. The wood varies remarkably in different 
locahties. 

Vessels (fig. 42, v.) in early wood {e. w.) usually from 3 to 5 rows 
deep. They are either round or elliptical and about 0.25 millimeter 
in diameter. In late wood (Z. w.) the small vessels have thicker 




Fig. 42. 



Fig. 43. 



Fig. 42. — Red oak (Quercus rubra). Transverse section through parts of two annual rings of growth; e. w., 

early wood; /.»'., late wood; /. p. r.. large pith ray; s. p. c, small pith ray: t>., vessel; «•./., wood fiber; 

ic. p.f., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 43.— California live oak (Quercus agrifolia). Transverse section through two annual rings of growth; 

a. ?■., annual ring; Z. p. r., large pith ray; s. p. r., small pith ray; y., vessel; w./., wood fiber; w.p.f., 

wood-parenchyma filler. Magnified 20 diameters. 

walls and form from 3 to 6 radial rows extending across the width 
of the annual rings of growth. The size of the vessels gradually 
diminishes from the early to the late wood. Tliis is a constant 
character and may be rehed upon in separating the red oak from 
the white oak. In the latter the pores diminish abruptly. The 
average diameter of small vessels in late wood is about 0.08 milli- 
meter. Wood fibers (w. /.) compose the bulk of late wood. They 
have rather tliick walls and moderately large cavities. The average 
length of the fibers is 1.19 millimeters and the average width 0.018 
millimeter. Wood-parenchyma fibers (w. p. f.) are scattered rather 



CHARACTERISTIC'S. 51 

irregularly throughout the annual rings of growth and surround the 
large and small vessels. They also form narrow tangential bands 
in the late wood. Pith rays: Large pith rays (Z. i?. r.) are usually 
from 1 to 3 millimeters apart. Small pith rays (s. ]). r.) are very 
numerous and usually but 1 cell wide. 

The wood of this oak may be confused with Spanish oak (Q. digi- 
tata), scarlet oak (Q. coccinea), yellow oak (Q. velutina), pin oak 
(Q. palustris), and Texan oak (Q. texana). See description of ejich 
for special distinctions. 

30. California Live Oak {Quercus agrifolia Nees von Esenbeck). 

(Fig. 43.) 

Heartwood light brown tinged with red; sapwood thick and 
slightly darker colored. Wood hard, heavy, close-grained, and 
rather brittle. Kate of growth exceedingly slow, requiring from 15 
to 30 years to increase 1 inch in diameter. 

Vessels (fig. 43, v.) arranged in 2 or 3 radial rows between the 
large pith rays, showing very little contrast between early (e. w.) 
and late wood (I. w.). The absence of distinct tangential rows of 
pores renders it difficult to obtain figures on rate of growth. Ves- 
sels formed during the beginning of the growing season are usually 
larger than those formed later. Occasionally, however, the pores 
in the middle of the annual rings of growth are larger than near 
the inner boundary. Large vessels vary fi-om 0.15 to 0.25 milli- 
meter, while those near the periphery of the annual ring are only 
about one-half as large, and usually round, though sometimes 
slightly elongated radially. Wood fhers {w. f.) are, on an average, 
1.34 millimeters long and have exceedingly thick walls and very 
small cavities. They are regularly arranged throughout the entire 
width of the annual ring. Wood-parenchyma fibers (w. p. f.) in 
early wood cliiefly surround vessels. Near the periphery of the 
annual ring of growth these elements are arranged in numerous 
irregular, tangential bands clearly distinguishable under the com- 
pound microscope. The wood of tliis species contains more wood- 
parenchyma fibers per unit area than that of any other oak. It 
also contains a great many crystals of calcium oxalate. Pith rays: 
Large pith rays (Z. p. r.) are from 15 to 30 cells wide, from three 
to four times as liigh, and from 3 to 6 milhmeters apart. Small 
pith rays (s. p. r.) are exceedingly numerous and are composed of 
unusually large cells. 

31. Highland Live O&k {Quercus wislizeni K. deQsiwCioWe.) (Fig. 44.) 
Heartwood light reddish brown; sapwood thick and somewhat 

lighter colored. Wood hard, heavy, tough, moderately close-grained, 
and very durable in contact with soil. It is an evergreen oak with 
rather indistinct annual rings of growth, the boundaries of which 



52 



TDENTTFTCATION OF NORT?T AMERICAN OAK WOODS. 



can only be seen with the aid of a pocket lens magnifying 6 or 8 diam- 
eters. Rate of growth moderately slow, requiring from 12 to 15 years 
to grow 1 inch in diameter. 

Vessels (fig. 44, v.) in early wood (e. w.) from 1 or 2 interrupted 
tangential rows, gradually diminishing in size in late wood (/. iv.), 
where they are arranged radially in single or double rows across the 
annual rings of growth. The average width of vessels in late wood is 
about one-half of those in early wood. There are 2 or 3 distinct 
radial rows of small vessels between the large pith rays. Walls of 




Fig. 45, 



Fig. 44.— Highland oak (Quercus wislizeni). Transverse section through parts of two annual rings of growth; 

e. w., early wood; I. ?('., late wood; 7. p. r., large pith ray; s. p. r., small pith ray; v., vessel; w.f., wood 

fiber; w. p.f., wood-parenchyma fiber. Magnified 20 diameters. 
Fig. 45. — Canyon live oak (Quercus chrysolepis). Transverse section through three entire annual rings 

of growth; a. r., annual ring; I. p. r., large pith ray; s.p. r., small pith ray; v., vessel; w./., wood fiber; 

w. p./., wood-parenchyma fiber. Magnified 20 diameters. 

vessels very thick, especially in the outer part of late wood. Wood 
fibers {w.f.) about 1.16 milluneters long and 0.019 millimeter wide, 
with thick walls and exceedingly small cavities. Wood-2)arencJiyma 
fibers (w. y.f.) more or less evenly distributed throughout the annual 
layers of growth. Tangential bands not clearly visible with an 
ordinary pocket lens. Under the microscope they are shown to be 
irregular and greatly interrupted by wood fibers. Pith rays: Large 
pith rays (Z. p. r.) about 30 cells wide and from 2 to 3 millimeters 
apart. Small pith rays (s. p. r.) seldom more than a single cell wide 
and from 8 to 12 cells high. 



CHARACTEEISTICS. 53 

32. Canyon Live Oak (Quercus chrysolepis Liebmann). (Fig. 45.) 
Heartwood light brown or sometimes tinged with red; sap wood 

(generally quite thick) is sometimes darker colored than the heart- 
wood. Wood very hard, heavy, strong, and not durable in contact 
with soil. In manner and rate of growth this species approaches the 
eastern live oak. 

Vessels: The manner in which the vessels (fig. 45, v.) in the annual 
rings of growth are grouped corresponds somewhat to that in the 
eastern live oak, except that in the former they are more numerous, 
particularly the smaller pores near the periphery of the annual ring 
of growth (a. r.). Vessels are usually round and vary from 0.08 to 
0.2 millimeter in diameter. The walls of small pores are very thick 
and their cavities small. Wood Jihers {w. f.) uniforaily distributed 
throughout the annual rings of growth. They average 1.2 millimeters 
long and about 0.02 millimeter wide. The cell walls are veiy thick 
and the cavities small. Wood- parencJiyTna fibers {iv. p. f.) are scat- 
tered irregularly among the wood fibers. Near the periphery of the 
annual rings they are arranged in short tangential bands, seldom more 
than one cell in width. Pith rays: Large pith rays (l. jj. r.) are from 
20 to 35 cells wide, from two to four times as high, and from 0.3 to 
0.8 millimeter apart. 

33. Blue Oak (Quercus douglasii Hooker and Arnott). (Fig. 46.) 
Heartwood dark bro^v^^ or sometmies nearly black when exposed; 

sap wood rather thick and of much lighter color. Wood moderately 
hard, heavy, coarse-grained, often very brittle, and not durable in 
contact with soil. Rate of growth slow, requiring from 15 to 20 
years to grow 1 inch in diameter. 

Vessels (fig. 46, v.) vary from 0.05 to 0.25 millimeter in diameter. 
Individual vessels often extend across the entire width of the annual 
ring of growth (a. r.). These as well as the smaller vessels in late 
wood are surrounded by wood-parenchyma fibers, allowing compara- 
tively little space for the development of thick-walled wood fibers. 
Vessels have very thick walls, particularly the small ones in late wood. 
Wood fibers (w. f.) invariably found only near the periphery of wide 
annual rings of growth. They vaiy from 0.96 to 1.38 millimeters in 
length with an average length of 1.13 millimeters. Wood-parenchyma 
fibers (w. p.f.) scattered uniformly throughout, but are chiefly found 
bordering the vessels. They contain numerous crystals of calcium 
oxalate. Pith rays: Large pith rays (Z. p. r.) veiy numerous, from 
15 to 35 cells wide, from two to four times as high, and from 1.5 to 
3 millimeters ai)art. Small pith rays (s. p. r.) onXj a single cell wide 
and from 5 to 15 cells high; they are very irregular on account oi tlie 
small pores which they avoid. 

(For possible confusion of this wood with that of valley oak {Q. 
lobata) see description of the hitter.) 



54 



IDENTIFICATION OF KOKTII AMERICAN OAK WOODS. 



34. Tanbark Oa,k (Quercusdensiflora Hooker emd Arnott). (Fig. 47.) 
lieartwood light brown or tinged with red; sap wood thick, dark 
brown or often tinged with yellow. Wood very hard, heavy, strong, 
and close-grained. Old and slow-growing trees produce wood that 
is very brittle and not durable in contact with soil. Rate of growth 
slow, recpiiring from 15 to 20 years for the average tree to grow 1 
inch in diameter. 

Vessels (fig. 47, v.) arranged in rather wide radial rows which can 
be easilv seen on a smooth transverse section with the unaided eye. 



ar 




- L pr 






Vpf 



Fig. 40. 



Fig. ■!? 



Fig. 40.— (California) Rock oak (Quercus douglasii). Transverse section through IJ aimual rings of growth, 
o.r., annual ring; Z. p. r., large pith ray; s. p. r., small pith ray; ?)., vessel; )/'./.. wood fiber; ;<'. p./., wood- 
parenchyma filler. Magnified 20 diameters. 

Fig. 47.— (California) Tanbark oak (Quercus densiflora). Transverse section through one entire annual ring 
of growth; a. r., annual rmg; s. p. r., small pith ray; v., vessel; w.f., wood fiber; w. p.f., wood-paren- 
chyma fiber. Magnified 20 diameters. 

There is no sharp contrast between early and late wood. The 
boundaries of annual rings of growth (a. r.) are indistinctly marked 
by a few rows of radially compressed wood fibres. Although vessels 
are usually larger in early wood, they are sometimes larger in late 
wood and gradually increase in number toward the periphery where 
the radial rows are branched. The diameters of the pores vary 
from 0.05 to 0.3 millimeter with an average of about 0.15 milli- 
meter. Wood fibers (w. /.) average 1.23 millimeters long and are 
most abundant in earlv wood and near the middle of the annual 



CHAEACTEKISTICS. 



55 



rings. Wood-parenchyma fibers (w. jj. /.) very abundant between 
the large pores, forming conspicuous radial rows across the entire 
width of the annual rings of growth. They are also arranged in 
single or double conspicuous tangential bands. The late wood is 
largely composed of small pores and wood-parenchyma fibers. Pith 
rays: Large pith rays (I. p. r.) from 25 to 40 cells wide and from two 
to four times as high. Small pith rays (s. p. r.) are only a single cell 
wide and from 30 to 40 cells high. In a transverse section they are 
very conspicuous when viewed under the compound microscope. 
The cells composing the rays con- 
tain considerable starch, tannin, 
and numerous crystals of calcium 
oxalate. 

35. live Oak (Quercus Virginia na 
Miller). (Fig. 48.) 

Heart wood light brown and 
tinged with yellow; sapwood'very 
thin and cream colored or some- 
times nearly white. Wood very 
hard, heavy, strong, and very 
durable in contact with soil. Rate 
of growth very slow, requiring on 
an average from 15 to 20 years to 
grow 1 inch in diamater. 

Vessels (fig. 48, v.) in early and 
late wood usually round and vary 
from 0.1 to 0.25 millimeter in di- 
ameter. Radial rows of small ves- 
sels so common in most American 
oaks are generally absent. Walls 
very thick, especially near the 
periphery of the annual rings of 
growth {a. r.). Wood fibers (w.f.) 
uniformly distributed and vary in 
length from 0.83 to 1.79 millimeters and about 1.39 millimeters in 
diameter. Walls very thick and the cavities small, thus giving to the 
wood its peculiar hardness and toughness which make it so valuable for 
construction purposes. The outer edge of each annual ring of growth 
is marked by 2 or 3 layers of wood fibers which are very much flat- 
tened radially. Wood-parencJiym a fibers (w. p. f.) occur in concen- 
tric bands around the larger vessels, but they are also arranged in 
irregular and inconspicuous tangential bands in late wood. The 
number of these bands varies with the width of the annual rings. 




Fig. 48. — Live oak (Quercus virginiana) . Trans- 
verse section through two entire annual rings 
of growth; a. r., annual ring; I. p. r., large pith 
ray; s. p. r., small pith ray; v., vessel; w.f., 
wood filler; uk p. /., wood-parenchyma fiber. 
Magnified 20 diameters. 



56 



IDENTIFICATION OF NORTH AMERICAN OAK WOODS. 



There are on an average about 10 such bands to each millimeter in 
radial distance. Pith rays: Large pith rays {I. p. r.) are from 25 to 
50 cells wide, from two to four times as high, and from 1 to 3 milli- 
meters apart. The small pith rays (s. p, r.) are seldom more than 1 
cell wide and from a few to 12 or 15 cells high. 

(For possible confusion of this wood with that of laurel oak {Q. 
laurifoUa) see description of the latter.) 

Table 1. — The lengths and widths of wood Jihers of the most important North American 



Species. 


Length. 


Width. 


Average. 


Maximum. 


Minimum. 


Average. 


Maximum. 


Minimum. 


(^uercus laurifolia 


Mm. 
1.342 
1.158 
1..300 
1.242 
1.063 
.921 
.979 
1.038 
1.121 
1.213 
1.267 
1.354 
1.229 
1. .521 
1. 325 
1.538 
1.308 
1. 154 
1.0.33 
1.433 
1.471 
1.646 
1.375 
1.488 
1.121 
1.354 
1.367 
1.300 
1.188 
1.358 
1.163 
1.204 
1.133 
1.225 
1.388 


Mm. 
1.875 
1.417 
1. 625 
1.542 
1.333 
1.417 
1.250 
1.250 
1..500 
1.458 
1. 625 
1.667 
1.417 
1.875 
1.708 
1.792 
1.667 
1.500 
1.417 
1.958 
1.833 
2.000 
1.625 
2.083 
1.375 
1.625 
1.583 
1.667 
1.458 
1.625 
1.375 
1.542 
1.375 
1.458 
1.792 


Mm. 

0. 958 

.875 

1.083 

.792 

.750 

.708 

.833 

.750 

.833 

.833 

1.000 

1.042 

.875 

1.167 

1.000 

1.083 

.958 

.917 

.667 

1.083 

1.208 

1.083 

1.042 

1.000 

.792 

1.042 

1.167 

.958 

.708 

1.042 

.917 

.917 

.958 

.958 

.833 


Mm. 
0.021 
.018 
.018 
.020 
.017 
.018 
.014 
.017 
.020 
.022 
.018 
.021 
.018 
.021 
.022 
.021 
.020 
.018 
.017 
.018 
.026 
.024 
.022 
.023 
.018 
.017 
.023 
.022 
.018 
.022 
.019 
.020 
.018 
.027 
.016 


Mm. 
0.027 
.019 
.019 
.023 
.019 
.019 
.015 
.019 
.023 
.027 
.019 
.023 
.023 
.027 
.023 
.023 
.023 
.023 
.019 
.023 
.031 
.027 
.027 
.031 
.023 
.019 
.031 
.027 
.019 
.031 
.019 
.023 
.023 
.031 
.019 


Mm. 
0.019 


gambelii 


.015 




.015 


lobata 


.015 


reticulata 


.015 




.015 


minor . . 


.012 


platanoides 


.012 




.019 


caUfomica 


.019 


alba 


.015 




.019 


breviloba 


.015 


phellos 


.015 


lyrata 


.019 


michauxii 


.019 


prinus 


.019 




.015 


imbricaria. . . . 


.015 


nigra 


.015 




.023 


digitata 


.019 


marilandica 


.019 




.019 


brevifolia. . . . . 


.015 


palustris 


.015 




.015 


velutina . 


.015 


rubra 


.015 




.015 


wislizeni 


.019 




.015 


douglasii . . 


.015 


densiflora 


.023 




.015 







o 



^c '12 



